I'm a preschool teacher and a mom (who works...) so I'll give you my perspective.
If he's been fever-free, below 100 (and that gives wiggle room for warmer temps, because some kids do normally run hot, but not *that* hot) for 24 hours, that's a definite "go back to school". In situations like this, I schedule sick care for my son in advance with our caregiver, so that if he can't go to his preschool, I can work. That said, from what you have described, if he's fever free and symptom-free since this morning, I'd probably take him in. If there are no symptoms (runny nose, vomitting, diarrhea, coughing, rash, etc.) chances are he's past being contagious.
Just be sure to take his temp about an hour after he wakes before taking him to school. Be sure he has a good night's sleep, too. As a teacher, I can see how much work school is for our little ones even on their healthy days. And once again, if you can, schedule the sick care (I know this isn't an option for everyone.), so you have some choices.... you might decide a caregiver is preferable to sending him. I've done that on more than one occasion. And it costs less than losing a day of work!