You did the right thing. If you start being lenient, then parents will expect you to be lenient. If they are not forthcoming it's actually pretty obvious. A child who has been "dosed and dropped" (given meds to mask a fever) will start to show symptoms again within about 4-6 hours of dropoff because that is when meds wear off. so usually right before/after naptime for me, I keep an eye out for this at this time of year although my dc parents have been pretty good.