In a predicament, not sure what to do

I am currently a Y14 (NI) Student who is preparing for A-Level exams commencing in May 2024.

This summer, I am fortunate enough to travel Europe for 2 months with a small group of friends. Because of this, I began looking for employment in January to help fund my travels. Due to demand being scarce, my only option was a small local store, who were looking for staff to help during the summer season. In my interview I did mention how I would be out of the country during summer, however they mustn't have picked up on it.

With exams coming closer, and closer, I decided that it would be in my best interest to put all of my focus into my exams, to help boost my chances at attaining the grades required to secure my spot at University. However, I am unsure how to go about notifying my employer, the store is small with a staff of 5 people, including the manager. I have been fully trained and equipped with uniform, so leaving at this stage feels like a **** move, however - it is my A-Levels on the line, which I see as more important than a part time minimum wage job.

I'd appreciate any advice on how to approach the situation

Thanks