My experience with my DYS DS9 is that he can be "lazy" and just does bare minimum sometimes. For example, in his writing class, he got a B in the first term. I asked the teacher why he got a B and what he needed to be improving on. The teacher said that she knows that he has the ability to produce much better work(he writes more descriptive and in more detail in creative writings). But many times, he just wrote short and simple sentences without putting in any effort. I had a talk with him and he improved in the second term and got an A this time.
So I agree with aquinas and Dude that you probably want to have the conversation with the teacher to find out more about why she had the conclusion that your DS is "lazy". You may find out that it could be the topic doesn't interest him or everything is still too easy in the gifted class that he doesn't think putting in full effort is necessary, or else.
