Byron's progress at school surprisingly improves as the novel progresses. In particular, he does very well once Mark is arrested and placed in the formatory. Byron himself states that he is taken aback by how well he is doing, and the reader is left to imagine that he is doing so well at school precisely because hard academic work is needed to prevent him from dwelling too much about what has happened and his relationship with Mark. Note how Byron talks about this:
The next months were a blur--I went to school and went to work and went home and studied. I ended up with straight As that semester, something that surprised me more than anyone, because I couldn't remember a thing I had studied.
Although Byron does very well in his work that particular year, he doesn't hold out much hope for continuing with similar academic success. The last two paragraphs of the novel state that Byron has given up on work and on trying to do well. He says "I don't seem to care about anything any more," and thus the reader is left to conclude that although he has done well in that particular year, this may well not continue due to his disillusionment and disengagement with life because of what has happened with Mark.