back to school pant (Mattapan, ma)

My son is going into the fifth grade. I am all set with supplies but need help with his pants. His uniform shir is bright blue but he can wear kakhis and sweats that are black or blue he’s already a 14/16. We live in mattapan a we don’t have a car, but I will travel with the kids on the bus in Boston. Gently worn pants are gladly accepted any help would be soooo appreciated 🙏 ty