In well running high schools, where the regular classroom teacher has autonomy, it is rather easy to fail students based on their academic performance. I have been able to do this freely for 6 years across three different high schools.

Where problems start is when students are identified as Special Education and have an Individualized Educational Profile (IEP) based on their academic or emotional "disabilities". The rules for these students are different. The consequences of not passing these students can be very costly (in court) for the school community and thus the tax payers.

For example, I have students that have an IEP that mandates they get modified tests, get to see essay questions before the test, get answers keys to all classwork and homework assignments, etc. It is viruatlly impossible for me to fail these students when I am obligated to give them a "modified" test - or and they are allowed to make unlimited test corrections until they pass the test!

What is truly amazing that students still manage to fail under these circumstances!

Now my district will fail these students, but the paperwork involved in properly documenting said modifications and eventually failure can be burdensome for some districts and eventually results in advocates suing the school.

Like I said, my district does fail these students, and does document.

Other districts, especially large urban districts, take a different route because of past/current litigation.