Just because to you its a joke, doesn't mean to others it isn't worth something. Remember that, some people have to work very hard to deal with Life, and HS and to come out on top in those situations with good grades is a very good reason to hold your diploma high and be proud of that achievement. But because you don't care about it you assume its worthless to everyone, or of no use in society.
As i stated before, that diploma is worth A LOT to many kids around the world. You should never devalue education of any kind, it is the single most beneficial thing you can ever have on this planet and what separates us from animals.