Your Kid can Fake it.
Faking sick that is. Billy's kid didn't go to school today, home with a 103 fever. I heard about that and immediately thought, "He went too far faking the fever." The point is to alter the thermometer enough to stay home, but not enough to have to behave like you're sick.
Well, turns out he WAS sick, but haven't we all tried to play the system? My kids do it remarkably well. Katie knows just enough to get to the nurse's office (a cough) but not so much that she gets a call home (Clue: Don't say 'headache' that only brings the call home for approval for administering of aspirin!)
When I was a kid the thermometer-on-the-lightbulb was always good for a day home, as long as you didn't hold it there too long, and it was accompanied by a mysterious but not-too-severe stomach ailment. Once after we moved to a new house, with radiator heat, in a pinch I tried resting the mercury on the steam release, but 104 tipped off my mom and my career was done. No more sick days, it was truancy from then on!