Basically you just need to show up at least half the time and you will get your diploma. The high schools, at least the public ones, just want to move you through and out.
Worse than that. Much worse.
Many of the urban public schools have a policy of "social promotion". Even if they hardly ever show up; even if they never pass a test - they go to the next grade, the following year.
They will also get a diploma at the end of twelfth grade.
What's amazing about this story, is that the young lady not only knows that she didn't qualify; she admits that she didn't qualify.
I've been in many high schools on the South side of Chicago. The typical belief there is that if they gave you a diploma, you must be qualified!
Magic! Or osmosis. Or something.