I think Brandon felt he had a lot to prove, with Jim's high expectations of him.

So yes I can see why you'd say that

Dylan had no parental figure to answer to, so he grew up much quicker and was very outspoken as a result.

Any time Brandon tried to tell Jim that he was struggling in school, he wasn't taken very seriously. I think it's sad. It also explains why Brandon kept his gambling addiction from Jim for so long