If people don't listen to what you are saying,stop talking to them.If people don't appreciate your ideas and respect your opinions,leave that place.It is not really about the fact that your ideas or views are not good enough,it is about the place you are in.Change your surroundings,even if it means leaving those people, even if it means changing your class,school or whatever.It is better to leave than stay in the same place till you are convinced that you are not good enough.It is called having respect for yourself.