I mean, hypothetically, let's say that a student never attends class, just aimlessly wandering the halls (which I'm skeptical about, but let's go with it). Then even if they somehow game the SAT and get into a good college, then what? If they're basically uneducated upon entering college, then it seems like, best-case scenario, they'll get like 4 years of education in college -- making them analogous to a student with a gradeschool education, right?
I mean, this sounds like a smoke-and-mirrors scheme.
But there are other students in such schools, however, that are trying to make the best of the situation they're in and these students want to go to college. Sadly, these school is so busy with discipline and attendance issues that it's almost impossible for serious students to get prepared for college.
And yes, there are many public schools that would appear to a visitor as chaos. Students do just roam the hallways if they don't feel like going to class. There can be so many doing this that it looks like they're changing class-- all the time. Not exaggerating.
For some schools it is a real problem. My girlfriend works at a pretty bad high school and she has tons of students who keep failing their classes because they never show up and the principal literally wanders the halls himself to try and force kids to go back to class.
There are schools where ~1/3 of the students just wander the halls aimlessly instead of going to class, where teachers turn over at a rate of 25%/year. In such schools even students who intend to go to college are going to be utterly unprepared for the SAT. These students actually need a prep course.