When I was 13 I also made sexualised drawings of my female classmates. I was showing them to a buddy and the teacher confiscated them, even sent a copy to my parents. What a douche, right? Good thing my drawing skills are bad enough so nobody knew who I was drawing haha. I don't even remember my parents reaction, I think they found it funny rather than concerning. Which is kinda understandable because the proportions were way off so the amount of cum I had to draw was ridiculous.
My point being, boys will be boys, punishing this is highly unnecessary.