how to be taken seriously

So there is this annoying, immature guy in my grade and he totally doesn't respect me or anyone else. He comments if girls have leg or armpit hair and is wayyyy too open about if he thinks girls are ugly. Some days I wake up feeling myself and then he will make some comment about my smile or my height, two things I am insecure about, and it just ruins my day. I am so tired of guys with no filter who can't keep their mouths shut when they have hurtful opinions that really don't need to be said out loud. I honestly just want to shut this guy out but it is so hard with him constantly around. I have tried to tell  him before but he always just laughs it off and tells me I am overreacting. Am I overreacting? What should I do to get him to start taking me seriously?