As others have said, your grades and your health should come before robotics. That said, I don't think there is such thing as over-dedication, there are just different degrees of dedication. The only problem I can see from being extremely dedicated is that if the others around you aren't learning or aren't involved as much as they want to, when the super dedicated graduate from high school, the team might suffer from having them gone and disappear. Just remember to leave your team better off than when you found it. As you advance through high school, be sure that others on the team will be able to take over when you are gone. Hope that makes sense...it did in my head.
Eric