Have your kids played around with the serious power they have in the phrase "I don't feel well"?

Both my kids (8 and 6) have told their teachers they don't feel well with unverifiable symptoms (sore throat, headache, nausea). Then I rush to pick up the kids, accept my over the top shaming from the office staff (I cried this time, not my finest moment), and bring them home only to see they are 100% fine. What do you do to prevent this??

It's only happened once each but I'm worried it will happen again because the power to control your parents for three days and sit at home seems too tempting to pass up.