S.A.
I come from a long line of school teachers and I've never heard of children fainting for no reason.
I would inspect his diet that day, whether he may have been overheated, was he dehydrated....
I don't believe anyone faints for no reason. There is always a cause. It may have been something very innocent, but that would have to be determined.
Is he on any kind of medication? Is he anemic? Could he be diabetic? What was he doing at the time?