High school kids are dicks. Don't ever take them seriously. Your opinion, at that point of time, is influenced by very few things and mostly pop culture and the people around you. Things definitely improve when you enter adulthood, get more life experience and realize that stuttering is not something that can be controlled. People become more tolerant, not because they have understood what stuttering is necessarily, because they simply can't give two fucks when they have their own problems (this applies to almost everything, people just don't give a fuck after a point). There will be some dicks who will still laugh and make faces, but ignore them. They don't matter.