Hi - Here's a link detailing what kids don't learn when they are not challenged at school:
What Kids Don't Learn

While I agree that happy is good, I definitely would try to get your DS involved in something that will challenge him, and if possible, at the school level. I would worry that your DS might not think that school is a place for learning, and then when the chance to learn and be challenged in school does come up, it might cause some difficulties.