[Doxterpepper]

Is it not unreasonable to believe that some things worth knowing or doing (A) are worth the prerequisite work (B)? If your class on data mining requires fundamentals in advanced databases why is it unreasonable to require people have taken that course to ensure the whole class is on the same page? Besides in most colleges you can sometimes skip those prerequisite courses if you can demonstrate adequate knowledge in those prerequisite.

[cryptonector]

Did you not read TFA?

The issue is that a) it can be greatly discouraging or impossible to fit in the subject's schedule, b) a waste of time and effort if the requirement isn't that hard, c) there may be a better way: the a, b, a, b pattern, which is to say: do A until you need to do some of B, then go back to A until you need more of B, and so on.

The a,b,a,b pattern is the right answer in at least some cases.

[sverhagen]

I think it's important to realize that you're optimizing for different things. "a, b, a, b" optimizes for, let's say, "attention span", while "B, A" optimizes for some sort of efficiency. Not everyone's attention span or need for efficiency are the same.

[cryptonector]

If abab lets you start being productive sooner, then abab is more productive. It may or may not be more efficient than B-before-A -- I doubt we can conclude one way or the other in the general case, so I don't see the point in discussing the two approaches' efficiency.

[mcphage]

> while "B, A" optimizes for some sort of efficiency

What sort of efficiency do you think this optimizes for?

[sverhagen]

A perception of less time spent overall, perhaps. Or less loss/dropout from not being able to achieve A (for lack of B). I personally prefer "a, b, a", so I have to imagine.

[cryptonector]

On the other hand, if B-before-A is discouraging, then it may be very inefficient. It could act as a filter, but not so much for skill or any particularly useful personal attribute so much as "enjoys B-before-A well enough", which isn't particularly indicative of anything.

In general I do think that B-before-A is a very useful approach, but it cannot be the only approach. For one, it doesn't scale, not as the chain of Bs grows longer over time. We teach a lot more math to students today than 100 years ago, but almost certainly we're taking shortcuts that essentially amount to a,b,a,b -- how else can we manage the otherwise ever-growing cognitive burden of the sum of our knowledge?