A private school is exempt from the Section 504 and IDEA laws (the laws that you get a 504 or IEP under). They do not have to offer any accommodations or services at all. The fact that they deny her diagnosis is a red flag.
My opinion is that having low grades and being an emotional wreck all the time is far more detrimental than a 504 Plan or IEP. Most colleges today like seeing that a student with learning differences is using the accommodations available so they can succeed. And you do need them if you want accommodations for SAT and ACT testing.
It is really too early to be worrying about college though. Right now, you’re daughter is having a really hard time. What is going to help her with that? The answer to that question is what you need to focus on.
ADDitude Community Moderator, Parenting ADHD Trainer & Author, Mom to teen w/ ADHD, LDs, and autism