We told her to keep him occupied, send him for photocopies, give him some extra tasks in class etc. but she doesn't want to do such things since my son sometimes improvise things and messes up.
Sorry for thread hijacking.
If there's any way you could get him into a school with other gifted kids, it would be a wonderful thing. I realize that may not be possible.
In a few years you might be able to get him started on Khan Academy (https://www.khanacademy.org/), but I guess at 7 he's still a bit young for that. There may be other online resources that would work, though... look around.
And as someone else mentioned, homeschooling might be an option.
In any case, I would suggest encouraging his interests and (particularly at this young age) not worrying about the subjects he's not interested in.
If he needs to burn off some energy, permit me to recommend my favorite sport: table tennis. It's a great sport for kids, and 7 is not too young to start learning it. Just a suggestion.