[olefoo]

Actually if taking attendance takes 5 minutes of class time (which it easily can with a class size of 30), then all students are blocked from being taught while the teacher is busy so it does make sense to count that as (n+1) * 5 minutes where n is the number of students.

Fingerprint scanners for attendance would both speed up and parallelize this operation.

[cma]

What could possibly go wrong with implementing a complicated biometric fingerprint scanner based system for our schools?

http://news.ycombinator.com/item?id=1221068

[olefoo]

Well card swipes are obviously unworkable. You could maybe link it to student's mobile phones...

But the real solution is to have decent schools with classes small enough that the teacher doesn't have to take roll call because they know everyone.