RebE, could you clarify what your Rebbe said – was he concerned with learning material? grades? just general attitude? school overall test (I don’t think there was this pressure on schools at your times)
To the OP question: we have a definition that Torah is someone’s occupation meaning a person spending all available time off work in learning. So, if he comes home from work and watches TV for an hour, he is not. If he stayed an extra hour at work instead, then he is.
So, same for a student: if he is busy learning material relevant to parnosa, ensuring that he will not join listim, then he is a ben Torah. If he wastes time in some way, then he is showing that he is not.