The levels are named each letter of the alphabet. As they pass one level they move to the next. As they pass addition, they move to subtraction, then on to multiplication and finally division.
In our building each level has it's own reward. If the child passes the letter, they get to stand on their chair and the class gives them a chair cheer (really, REALLY loud screams, cheers, banging on the desks, what ever makes a loud noise!)