Grading in Schools

We have grades in schools to tell us if we're doing well or not. Therefore, why do we have number grades instead of standard grades. Standard grades are simply if you're doing well it says you're advanced, if you're average, it says average, if you're slightly below, you're slightly average, and if you're far below, you're potentially average. This makes more sense than number grades, because number grades are trying to put you into these catagories, but it's more accurate if you simply go by the standard system. The current system is not nearly as accurate, and will hopefully be changed in the near future. That is my opionion on grading systems.