We're talking about passing, not succeeding in, high school classes here. There's either a history of borderline/failing performance in school or a severe lack of effort on the student's behalf. I guarantee you three things: 1) The teacher was aware. 2) The student was aware. 3) The coach did not care enough to involve themselves in the education of these student athletes.
The blame for academic failure is on the student and teacher.
The blame for ineligibility ignorance is on the coach. Seriously, how many players are there to check on?