Khan Academy

I almost feel like reviewing Khan Academy is unnecessary, it has been so prominent over the past few years. However, it is one of the most impressive online resources for learning, and I like it, so this site would be incomplete without it. Khan Academy is an enormous, diverse, and free collection of online lectures across an equally enormous number of subjects – in their own words “from math and finance to history and art.” Plus math exercises, an interactive computer science section, and the potential for much more. Khan Academy is a rapidly growing . Because they are constantly adding new lessons, and expanding features, this article will probably be out dated by the end of the year, if not the week.

Aesthetics: 8
Entertainment: 6
Usability: 9
Bonus: Huge number of subjects!

Note: Almost exactly the day after I posted this Khan Academy updated their interface. I have updated the first image, but the rest of the screen shots below still show the old interface.

If there is a subject you want to learn about, it is probably here. The majority of the material is video lectures – usually 4-10 minutes. In the videos, the teacher, often Salman Khan himself, speaks over a visual presentation to explain the subject. While I haven’t seen many, those I have seen are quite good. There has been some back lash (see the links at the bottom of the page), and it is key to note that Salman is not a professional teacher, nor a certified expert in every subject he covers. However, he is smart and he speaks in common language that I think is accessible and accurate. Khan academy shouldn’t replace school, or college, but these thousands of lessons are a great place to start with any subject. But wait – there’s MORE!

Khan Academy Home Screen Shot

The home page – look at all that stuff! In the top left you’ll see a drop down menu, with a link to the knowledge map.

Mathematics exercises, with a map! These can be accessed by searching for the material, or via the knowledge map (see above to find your way to the map; look below for a picture of the map).

Khan Academy exercises are great for sticky subjects students are stuck on, need to review, or just practice. Problems come as straight numbers, and sometimes word problems, with randomly generated values. In my experience one of the most mechanical and time consuming tasks for a teacher or tutor is generating problems that make sense and solve with a clean/neat answer. Not only do these exercises vary the numbers, they include “hints” that gradually walk though the problem, and then reveal the answer.

Khan Knowledge Map Screen Shot

Look at all that knowledge!  One complaint I have is that the knowledge map doesn’t zoom out very far – to get this screen shot I zoomed out by pressing Ctrl and the minus key, use Ctrl + to zoom back in.

The problems come in “stacks,” illustrated by the stack of cards (see below, top right).  Student can score a 1-3 leaves on each card. 3 leaves for a correct answer on the first try, 2 for a second attempt or with hints, 1 if the answer has been revealed by showing all the hints. At the end of a stack the number of leaves is shown, plus the number correct in a row, plus the number answered “quickly”.

A Khan Exercise Screen Shot

The Scratch pad allows students to do work on the screen, and then they enter their answer on the right. Here I have shown all the hints to the problem, just to illustrate, but showing all the hints results in a maximum score of 1 leaf.
Khan Results
The fire cards shows the number answered quickly, while lightning indicates the longest streak of correct answers, and leaves shows the number of points earned.

For more information on Khan Academy check out the links below.

If you like Khan Academy, you might also like:

Some of coolest videos on Khan Academy – under construction – suggest one in the comments!

Criticisms of Khan Academy

Among teacher and education innovators there is a huge amount of criticism of Khan academy. The reason for this is the mainstream media’s unchecked exuberance for the site, which overlooks major flaws and growing pains inherent to the website. Some examples below:



CellCraft is a free cell biology game available online (full screen swf) or for download/offline. The game covers the very basics of cell function and organelles, at about the level I learned in middle school. Terms that were well covered include nucleus, ribosomes, RNA, ER (Endoplasmic Reticulum), peroxisome, lysosome, Golgi body, vesicle, fatty acid, amino acid, glucose, nucleic acid, as well as others that are less central to game play. If you’d like to see the whole list, select the full screen link above and flip through the encyclopedia – or better yet, play the game. I think that taking it slow the game could take 2-3 hours depending on the player, I managed to blitz though in about 45 minutes, but that didn’t leave as much time for learning.

What I love about this game is that it really is a game. There are characters, a story, jokes, and a serious chance to fail – even if failing just means restarting the level. Which means that kids learn without ‘studying’ because the game play depends on understanding that ATP is fuel, and lysosomes dissolve things, etcetera. To top it all off, the game is pretty. It’s not cutting edge, but it looks slick and runs well (some hosting sites glitch out about 2 minutes into the game, but I have not had that problem with the links above).

Ease: 10/10
Aesthetics: 10/10
Entertainment: 10/10

CellCraft Level Select Screen Shot

There are eight levels, each of which gradually introduces more organelles and their functions

This game was designed with middle school students 11-13 year old in mind, and to be potentially useful for high school students aged  14-18.1 It would probably not be very useful in a college environment, but I cannot imagine a more useful tool for starting off a middle/high school into to biology course unit on the cell.

It is important to understand that this is a game, and like all games it involves fantasy. Fantasy in games can come in two forms – exogenous fantasy or endogenous fantasy.2 An exogenous fantasy has nothing to do with material and could be used to teach almost anything. Example of an exogenous fantasy include hangman, the classic game concentration/memory, the games scatter and space race at Quizlet, or anything found here. The problem with exogenous fantasy is that it is less compelling than an endogenous fantasy, and is less effective at getting the user to really engage in the material.

In contrast, endogenous fantasy is woven into the game itself – meaning that not everything that is said is literally true, because there is a fictional story driving the actions of the player. CellCraft is such a game. For instance, there is no reason to believe that the platypus originated on another planet, or anything else in the plot of this game. Also, you cannot just drop organelles into cells, and everything in the game is simplified to make the mechanics of the game work. BUT if you want kids to remember things like ATP is cellular fuel, and that it comes from glucose, and that glucose is more efficiently turned to ATP by mitochondria, this is a great game. A follow up lesson will probably be necessary to clear up questions about what is and isn’t realistic about the game – but that should not be a problem.

I would recommend it as a homework assignment, with an alternative worksheet for those who can’t or wont play, and including the encyclopedia as required reading. Then, have the students write out questions about the game, and take a quiz to make sure they actually played it. There will be some explining to do, but anything that gets kids to ask questions is a good thing, at least in my book.

Cell Craft Level 8 Screen Shot

Level 8, with a lot of the organelles installed and functioning. Played on Kongregate (the online link) which allows saving progress but that requires registering account.

Released July 2010

1See AnthonyP’s comment.
2 Loyd P., R. (1996). Seriously considering play: Designing interactive learning environments based on the blending of microworlds, simulations, and games. Designing interactive learning environments based on the blending of microworlds, simulations, and games, 44(2), 43-58. Retrieved from – See the section on games.


Seterra is a geography quiz game. With quizzes spanning geographic features, countries, capitals  and cities Seterra knows a lot more about world geography than I do, but it’s a great teacher. It is available for download or online, the primary difference being the volume of advertisements (3 online vs. 1 offline).

Ease of use/intuitiveness: 9
Entertainment value: 3

Seterra African Country Quiz Screen Shot

Me, failing a quiz about African Countries. A correct 1st answer colors the country white, 2nd attempt pale yellow, 3rd attempt bright yellow. On the 4th attempt the target country flashes red, and is colored red once selected.

The strength of the program is its simplicity – especially off line, the user is presented with a simple, clean interface with few distractions. On line is a little more cluttered, but still easy to use. The visual fed back of coloring the countries is very well done, although I would choose a color other than white to symbolize success – maybe overlay the countries flag.

The 25 largest cities quiz, offline screen schot

The 25 largest cities quiz, offline. Before being answered each city is a small dot – look for Dhaka near Ghangzhou.

On the other hand, it is a very simple program that could be further developed. It was first released in 1995, and that is probably why it  is so elementary. Modern students would probably benefit from a bit more flash, maybe more detailed maps with some geography – satellite photos would make a great wow effect – or the option to use night pictures where the lights of cities could be seen.

Other additions would include some integration of international news feeds with current events, and the option to use historic maps. A way to organize classes and track progress (something like Xtramath’s teacher interface) would take this program to the next level.

That said – anyone looking for an easy, relatively pain free way to learn or teach international cities, countries, and geographic features will find that Seterra is exactly what they need.

The menu of Seterra (offline) screen shot.

The menu of Seterra (offline). The game was developed in Sweden, and has much more comprehensive options for Europe, but there is still an impressive amount of information across the globe.

Also check out these other free-ware products from the same designer (who happens to be the author of

  • Sebran (early education)
  • Selingua (language vocabulary)
  • Sephonics (spelling and phonetics – probably best suited for linguistics students)


My first recommendation is, for memorizing basic addition, subtraction, multiplication, and division facts.

Entertainment: 6/10
Ease: 9/10
Aesthetics: 8/10

Intended users: Teachers, Students, Parents – separate interface for each. Designed for both at home and computer lab use.

A screen shot of my class - all names removed and data scrambled.

A screen shot of my class – all names removed and data scrambled.

This website does one thing, and it does it exceptionally well: fact fluency.  Fact fluency is the ability to quickly recall an answer from memory without computation. Specifically, Xtramath works on users ability to recall addition, subtraction, multiplication, and division facts from 0+0=0 to 144/12=12.  The reason this website is so great, is that fact fluency is fundamental to learning math, and also excruciating to teach – but Xtramath is a fast, effective, and easy solution.

The ability to quickly recall these answer is critical, not only because it speeds more complicated operations, but because it also instills confidence. One of the greatest things a math teacher ever did to/for me was make me take timed tests converting fractions to decimals. That was fifth grade, and, of course, I hated her for it. I complained about it for years, all the while reaping a huge advantage over less lucky peers who struggled with both fractions and decimals because they failed to see the connection. In contrast, I thought I was naturally gifted with fractions and decimals. At least I was .5 right.

The advantage to fact fluency versus re-computing arithmetic every time is hard to overstate.  Fluent students spend 0-2 seconds solving 7*8, while non-fluent middle school students can spend 40-90% of their time for each problem performing basic arithmetic functions – or worse, running to a calculator to punch it in. That lag time slows learning and prolongs misunderstanding. Half the time they’ve forgotten the original problem before they retrieve the fact.

In neuro-geek-speak: the lag time weakens reinforcement of correct intuitions, while errors build an unreasonable aversion to practicing advanced concepts. This can be especially painful during class practice, when teachers cannot spare the time to locate the error behind a verbal wrong answer. Suddenly, despite understanding the concept at hand, a student’s arithmetic error can become a full-blown public failure. This is where Xtramath comes in.

The traditional method of teaching fact fluency is a combination of chanting, flashcards, games, and timed test – all of which can be painful. Don’t get me wrong, they work, but they are boring, or stressful, or both at the same time. Xtramath has three major advantages over the old ways.

  • It is shame-less
  • It is less boring, because it is tailored to the student, and
  • It feels like learning, because you are learning

To elaborate, unlike answering a question out loud in class, chanting with a group, or competing in teams, there is no one standing over your shoulder when you do Xtramath. Unlike a timed test, there is no grade and no one grading. That means no pain in getting it wrong – just a quick prompt of the right answer, type it in, and the mistake is behind you.  Stress is bad for memory, so why should learning be stressful?

Screen shot of a mistake.

A mistake in Xtramath prompts the user to put in the correct answer immediately, and then move on to the next question.

At first I wasn’t that impressed with Xtramath because it was “just” another flashcard web site, and on some level it is.1 However, Xtramath is distinguished by its laser-like focus, and a smarter algorithm. Flash cards are perfect for fact fluency, because recognizing visual cues and regurgitating the answer is the objective. More significantly, Xtramath repeats problems that are students are slow to answer and those they get wrong. Not only is this a more effective use of students time – it’s less boring, and boring is also bad for learning.2

Which brings me to my third point, Xtramath is brief. Every time students log in, they are prompted to do 2-3 sets of “cards”. This means that students don’t get tired, yet they get the reward of being finished if they stick through 2-3 sets of 25-50 questions.3 I don’t know if they tested and optimized it, or if the teachers who made it just knew from experience – maybe it detects boredom via slow-down and errors. In any case, Xtramath manages to push students into a substantial amount of practice, with out being overwhelming. Learning theorists have long known that splitting up practice is more effective than the same amount of time spent in a single session. This is known as the spacing effect, and it is one of the oldest, most robust, and most substantial principles of behavioral science.  If need be, students can quit at any time by closing the window, and they want they can log back in for another session as soon as they want.

(a list of flash card websites is on my to-blog list)

Craig, S., Graesser, A., Sullins, S., & Gholson, B. (2004). Affect and learning: an exploratory look into the role of affect in learning with autotutor. Journal of Educational Media29(3), 241-250. doi: 10.1080/1358165042000283101

a rough estimate – I have tried the system my self, and I know it is a sizable number per set, but I don’t have any exact measurements.

**** Pavlik Jr., P. I., & Anderson, J. R. (2008). Using a model to compute the optimal schedule of practice. Journal of Experimental Psychology: Applied14(2), 101–117. (Text).

*****Dempster, F. N. (1996). Distributing and managing the conditions of
encoding and practice. In R. A. Bjork & E. L. Bjork (Eds.), Memory (pp.
317–344). New York: Academic Press.