IDK if its changed in the last fifteen years since I left school Yorkie, but they made it very clear you were in the top set(science we were only one that did individual sciences as opposed to double award, maths we were only ones to do the extra module that was more A* orientated, English we were told bluntly by the teacher). All the other sets were described as "mixed ability" but I know they did group a "bottom set" together in maths and science (they were in next room to us) even if they didn't call it that.