Those are probably graduating seniors %'s. The following suggests that it is probably worse than what you posted.

The Freshman class in most High Schools is the largest class.
Now if you take the number of Freshman that you started with, and then look at how many kids graduate... those numbers would be much lower.

There is a big lost group that no one ever talks about. The Freshman class at the High School where I teach was right at 1000. The number of kids that graduated was 760. Our official % graduation for the senior class was around 95%, in other words we had very few seniors that did not graduate.

Where did all those freshman go? You might expect the ones that left for whatever reason (moving, etc...) would be replaced by others moving in. But they are not. So what happened to the net 240 kids? Ya just dont hear about that.

Well at 16 years old in this state you can quit High School.