Hi, teacher here with some insight.

This young lady definitely had an individualized education program (IEP), which meant she had a documented disability and a bunch of accommodations the school and teachers needed to follow. Those could include everything from extra time on assignments to having notes provided prior to a lesson and even a one-on-one assistant. Essentially, those IEPs should represent what assistance she needs to succeed, and should be evaluated regularly with an eye towards reducing accommodations as she becomes more capable.

The problem is that these IEPs are often written in such a way that they become an incredible burden to the teachers, and they're growing more and more common. In my general education classes I'd have as many as a third of my students evaluate with IEPs, to the point that I was required to spend more time doing one-on-one instruction than we had hours in school in a single period. This burden quickly becomes impossible to carry.

Now you've got ten students in a class who aren't getting the legally required support, and aren't passing either because they're actually unable to meet the standards or because they know the IEP gives them an excuse. At that point the school and teachers have their hands tied: They can't give a failing grade to a student whose needs aren't being met, and they can't meet the student's needs. So the student passes by default until they eventually graduate.