I can't remember when we started doing algebra, but I'm prettty sure GSCE maths, which all 14-16 year olds had to take, included algebra of the sort 6x+5=17. There are times when having an unknown quantity is useful (diluting the orange squash, perhaps).
I think here it's good that you can leave school at 16 and still have some sort of qualifications, even if you don't want to waste any more years of life in school.