My mom has a really powerful bullstuff detector.
If I so much as just say "i have a headache" then she immediately goes and asks me if I have any projects or stuff due that day or any tests or whatever. I once threw up and I still felt sick and she made me go to school. Thank God I didn't throw up again.
My dad? He just asks if I can make it.
If I really can't, then I can't.