Yikes, at 13 dh would have made sure ds was up first time he was called, point him in the direction of the shower and would put breakfast on dinning table for him and made sure he was down to eat it. If he regularly didn't want to get up an earlier bedtime would be suggested. He wasn't keen and would pass on cereal/toast, so we tried different breakfasts and porridge/fruit or eggs/beans/bacon or sausage were more popular.
now at 15, he doesn't like an alarm so weekdays we knock, pause (just incase 😊), open his bedroom door, don't look in, say morning and walk away. He gets up within a couple of mins, goes straight in the shower then - while dh showers - he gets dressed and microwaves himself a huge bowl of porridge (he puts oats/milk to soak in fridge overnight so he can just stick it in) and chops/mixes in a banana (all while watching youtube 🙄). At the weekend we do a basic cooked breakfast.
Even then he is feeling hungry by 11am break, when he gets a roll in sausage. He now likes this routine and would struggle in morning lessons if he hadn't showered/eaten breakfast.
13 is still young enough to be cajoling/steering, not forcing, them towards good habits, especially ones that set them up for a good morning in school when they are working towards exam year, too young to leave them to it if they haven't developed them yet.