The school year is almost over here where I live.
Within the next month or so, there will be a news story about the high school graduation rate in the local press.

The way high school graduation rates are reported locally is by taking the total number of high school seniors that graduated and dividing it by the total number of seniors that started the school year.

That is a false number. It is a false high school graduation rate.

The correct way to calculate the high school graduation rate would be to take the specific freshman entering class from 4 years ago and compare how many of those exact people graduated this year (as in, they didn't drop out. Moving away removes them from the calculation).
Here locally, using that method reduces the graduation rate to about 55%. That darn sure isn't the number reported by the school board and mimicked by the local press though.

If you see a story in your locality about high school graduation rates, take a good look at how they calculate their numbers.