Jason — just in fairness, I wanted to note that the article does explore the question of whether other factors might explain the connection:
“There has been an ongoing debate about whether all these things linked to working longer hours are the fault of the work or the fault of other prior things that predict drug use, doing poorly in school and working longer hours,” says lead researcher Jerald Bachman, a professor and research scientist at the University of Michigan.
For some students, work may be an escape from an already failing academic record, says Steve Schneider, a school counselor at Sheboygan High School in Sheboygan, Wis.
Students who work intense hours “are those students who typically haven’t been successful in the classroom anyway,” he says.
I’ve seen studies like this before — it does seem to be the case that when you make a good-faith effort to find kids who are comparable in all ways except whether they work, working seems to hurt school performance. Of course, without random assignment, you can never control everything — at the end of the day, something made one kid work and the other not, and that something might also cause the academic problems — but I don’t think you can dismiss the finding out of hand, either.
In addition, I think it’s worth considering the non-academic benefits of low-skill work — character-building, interacting with customers and coworkers, and all that. I worked a lot in high school and college, and in retrospect I certainly wouldn’t trade that experience for a higher GPA.