First week back to school

It went smoothly. My son likes his new teacher and has mostly the same friends as he did last year in class. This year, my son is in the 3rd grade and wants to fit in with his friends. It is amazing how quickly they grow up and begin to learn about what other people think of them. Although I did get my son a few "popular" items, he understands, or at least he nodded his head, that people should like him for what's inside and not what's outside. How do you teach your kids to love themselves regardless of who else does?