I don’t remember who said it, but I heard that a Rav (and a prominent one at that), said, that if kids who are in a yeshiva where secular studies are part of the curriculum, it is bittul zman not to try your utmost.
that being said, not studying secular subjects as well is ridiculous. I am in 12th grade, and realize that it is MY RESPONSIBILITY to support my family. The Ketuba says it is my responsibility, not my father-in-law’s … to mooch off of him would, in my eyes, be disgusting