I would say that the question of whether your child is gifted or not has likely already been answered by his school. They're providing him with gifted services, so they must have assessed him in some fashion and determined that he required them.
And given that his knowledge/skills far exceeds age norms already, I'd say that no, the one hour of after-schooling is not necessary.
I hear what you're saying about not wanting him to spend all day in front of the TV or playing Minecraft, but we're only talking about one extra hour of the day, and it sounds like you're already doing a good job of making sure he gets some of the other things he needs... play time with others, exercise, etc. So:
1) Would one more hour of TV or Minecraft really be a problem?
2) Are there other things he could do with that time besides reading and math with you?
With an extra hour in his day, he could:
- Do art projects/puzzles
- Pursue an interest in science or history
- Play with other kids
- Learn a musical instrument
- Join a theater group
etc.
