Dear Mr./Ms. Bossname,
I am in an extremely awkward position and unfortunately must resign.
I took this job to help fund my college education and also because I have a strong work ethic and believe in paying my way. However, I recently learned from the Financial Aid Office that if I earn more than $XX, I will become ineligible for state-based grants. This would make tuition unaffordable for me. Instead, I can get a Work Study position on campus that would not have the same implications.
If possible, it would be great if you could consider keeping me on but capping my hours at ## hours per week. If you can’t do this, I totally understand and I apologize for any inconvenience.