When a child is not neurotypical and needs extra support, there are two avenues - the child remains in a mainstream school or the child will be sent to a specialist school. FAPE (the right to a free and appropriate education under the Americans with Disabilities Act) means that the aim is for a disabled child to have as 'normal' for lack of a better word education as possible. So the aim is to keep as many children in a classroom as possible but with a support system that enables this. A support system can mean pull-out academic support, social workers, school psychiatrist, an inclusion classroom with a second teacher with a special ed background, an aide for the student or other things. In many cases this works great. Of course the more adequately funded a school is, the better it works. Sometimes it doesn't work. Then the kid will be sent to a specialist school that can handle the kid's needs better. But this out-of-district placement is expensive and the school district has to pay for it. I live in an East Coast state with one of the best schools in the country and the highest property taxes and an out of district placement could easily be $100k for the year. So the school districts often try to argue that it is not necessary.
My child has a learning disability (and is getting great IEP services that are so supportive that it looks like they will learn the skills to operate without supports by the time they graduate high school so we are a real success story of a well funded system) so I can't really speak to behavioral aspects of the IEP system, only the academic side.
But it appears from what I have gleaned over the years that IEP students with underlying behavioral issues will get sent to talk to the social worker when they act out in class. That is step one. We have a child with fetal alcohol syndrome in the neighborhood and he was not able to function in a regular classroom. When he set fire to the school bathroom in elementary school, he was then placed out of district. My guess is that something needs to happen for the school district to take that action. So it appears you go through a system of escalation. But this is a system that is well funded and supportive. It appears that things are not like that in Newport News.
As to the parent in the classroom, I have never heard of that either. The only explanation/theory I have is that with staff shortages, the parent acted as aide because the school district was unable to hire one.
I hope this explains the IEP system a little bit. The student will have had an IEP. 504 plans are 'merely' adjustments to help you function during the day. For example, if you are blind the 504 plan will entitle you to books in Braille. Or if you have ADHD, you can get extra time on exams or preferential seating where you can concentrate better. I hope this makes sense.