How to go about quitting seasonal job early?

I was hiring for a retail position for the holidays and was told the position would run until mid January after inventory. That being said I start school again January 7th (which they are aware of) and I was hoping to be able to work while I was in school, but I just got my class schedule and between school and family responsibilities I won’t be able to balance everything. I want to give them a 2 weeks notice of some sort to let them know I’ll need to finish work before the 7th of January but I’m afraid it will ruin a future reference for me by leaving the position earlier than anticipated.

Any advice or thoughts on the matter?

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