I'll go ahead and be contrary to the OP and say that sometimes, yep, kids are lazy.
I'd want a whole lot more information from the teacher before I started weighing in on whether this is worth talking about, though. If your DS is doing the minimum required... what does that mean? In what context? And if he's meeting expectations... where's the problem? If he's capable of doing more and you want to push him, then increase the expectations. Or if you want him to do more than the others, what are you offering him to make it worth his while?
It could be that the really lazy one here is the teacher. But again, there isn't enough information here to judge by.
