Send the child home. Sometimes they just seriously need mom or dad to snuggle them and tend to them. Being sick enough to stay home doesn't always mean a fever or rash or obvious symptoms. The best indicator is a normally perfectly content child not being able to keep it together.

If you haven't sent the kid home 10 times already then I would think (hope) the parents understand and come get him so they can care for him.

Hopefully the weekend is enough time for him to recover enough to survive Monday with you!