advice for losing weight while in high school?

hiii!! i'm a senior in high school, and i've been waiting to lose weight for a while. i'm looking to lose around 15-20lbs, i'm currently 5'2 & 130lbs!! :D

but i've been struggling to stay in a deficit, especially while i have school. i don't know how many calories are in the school lunch, so i either don't eat it and end up really hungry, or eat it and feel guilty about it. and i usually end up eating a tonnnn after school.

i'm not really sure what i could pack for lunch, since i don't have much room in my bag and i don't want to carry a lunch box around (i don't have a locker). i would try to meal prep sandwiches, but my mom doesn't want to buy sandwich meat since "i don't eat it".

sorry for the yapping!! i'm just not sure what a good strategy for me would be, i'd love some advice!! :D