I always allowed the school age to bring their own nintendo - well it was Game Boy back then to play but it was also a privilege they could lose for rude behaviour, etc. Because it was their own it was up to them to take care of it and that was made clear with parents that I was in no way responsible for it and they had to take that on themselves. I only intervened if asked.
It was nice to have them more or less quiet off in the corner - protected from the little ones as in they weren't allowed where the big boys were.