Native wisdom--and our own memories of fooling, disobeyind and just generally tormenting substitute teachers--tells us that when the regular teacher is gone, not a whole lot of learning takes place. And in a rare confluence of academic research and common sense, it turns out this is true: Kids learn better the more their teacher is around. It's expensive, too. Subs make lousy pay, but it adds up.

So simple and yet so frustrating. according to a report in the latest Education Week. Because no matter what incentives school administrators offer--up to prizes of three-year car leases to teachers who cut down on sick leave and other absences--teachers continue to take about the same number of days off.

You'd have to expect teacher sick days to be higher than the norm...they work with crowded classrooms of sniffly kids all day long. Still, the more generous the contract is about allowing paid days off, the more days teachers take. (Conversely: Would we really want teachers showing up when they're sick, afraid of losing a day's pay?) And principals note that a disproportionate amount of illness seems to occur on Fridays and during Thanksgiving week. So what's the answer here? Doctors' notes, just like for the kids?