Can a charter school deny ABA for a student if the services are paid for by parents or insurance? I know, by law, regular public schools must allow PIP (private instructional personnel) to deliver ABA but a local charter school is denying this request. If charters are supposed to follow IDEA, wouldn’t they also have to allow PIP to deliver this service?

First, I'm not an expert in this field, so hopefully others will weigh in.  Charter schools are publicly funded, so the assumption would be that they do have to follow the IDEA.  However, private schools often receive public funding, as well, and have to provide (or in this case, allow) services, but not to the extent that public schools do.  It might depend on what the school's charter says.  It also might depend on what state regs say in terms of charter schools.  I would suggest contacting you state department of education and asking your question.

I have seen where schools provide ABA.  Public schools need to provide FAPE - free appropriate public education.  If the parent is paying and ABA is needed for the student's education to occur, the school should be providing the ABA at their expense.

It would also depend on if this charter school is a public school or a private school.  I'm getting the impression it's public based on the wording in your post so the school must provide FAPE.  In my area, I've seen schools say no to private instructional personnel so my guess is this varies by state - I'm in PA.  (Not enough detail to know 100%.)

8 hours ago, JSD24 said:

It would also depend on if this charter school is a public school or a private school. 

In the US, all charter schools are public, so FAPE and all ought to apply.