You need to tell your parents, a teacher, or an adult you can trust. You also need to rise above them. Anyone who would say something so mean is a total loser and will never amount to anything later on in life. These horrible people telling you this probably have terrible lives at home, are doing bad at school, and other things, so they take it out on you because they are too weak to face their real problems.
Just focus on people you care about it and your passions in life. Ignore those losers. Rise above it all. In the end they will be dragged down by their own hate and you will be the superstar.