I believe in school law and the way it was intended but it often doesn't happen that way. I would recommend you do the diagnostic out of the schools since Schools can and do leave out pertinent assessments that may make them provide more to your child. They have to pay for your doing assessments elsewhere if you disagree with their assessment, and also if you have diagnosed and documents, etc. as they can't play doctor. If you have a qualifying diagnosis for an IEP, they have the right to determine whether it affects your child or not to require an IEP but if you have doctors elsewhere that write this child would benefit from Speech, or needs speech etc. with scores reflecting...needs, from other assessments-they HAVE to consider. Any diagnosis that is not recognized as needing an IEP can be accommodated by a 504 which is a section of the law allowing them helpful intervention. The IEP usually doesn't go to college and leads into transitions but the 504 does. People even on the SPED team tried to tell me it doesn't but I went to the University with my daughter and took the legal document with me. My daughter had an anxiety disorder and was given her tests in another quiet and more distraction free place and was allowed more time too so in college, the instructors were told the student qualified for the special needs...and when the tests happened they had to leave her test at the SPED center and she had to show up there instead. There were some instructors that argued but the center said she needed to call them and they stepped in for her. In school the 504 is supposed to be honored like an IEP and they had to have meetings etc. I had some teachers debate the accommodations but I kept going to the school counselor and calling the principal overseeing the teachers who gave me a hard time and they do have to follow the law. With my daughter the IEP worked and the counselor and the principal were the ones who insured that it did when we struggled. My son's IEP has been a total miscarriage of his rights and intervention...which is another story and in our district requires an attorney, but they are supposed to still follow the law. Your child could get an IEP all the way through school and in H.S. have it made into a 504 to go to college too! If you see anywhere your child should have an IEP she should have it and I would never worry about it being "too small" this is rare...most of the time the schools worry about meeting the child's needs financially... the simple accommodations you are seeking are not really a problem. They may think your child is higher functioning than she is and never accommodate or meet her needs like with my child and that is where the problem lies, because they say we do not see that the child is affected by his diagnosis ... but your outside testing really reflects how much your child is affected then you have the advantage.

I know that there are also Advocates that can go with you to the school and assist in IEP meetings. Keep fighting for it. They have the tools and if you can get a diagnosis from a doctor or developmental pediatrician, that would probably be great. My son is almost 5, has an IEP and has difficulty with emotional regulation AND has social skills deficits. It's a real problem and these children deserve supports. Good luck.

CARS is a 15 point rating scale. I filled out 1 and the teacher from early intervention (that only saw him 2 hours a week) filled out 1, then a psychologist grades it. Based on the scores my CARS and the teacher's showed 2 different kids and was told "he doesn't qualify for the ADOS" (which is what I actually requested and they gave him the CARS instead.)
The advocate informed me that the CARS is just a screening tool and ask again in writing for the ADOS.
The ADOS is a semi-structured assessment that consists of various activities that allow a specially trained Psychologist to observe social and communication behaviours related to the diagnosis of autism. It is very structured and the psychologist was surprised at the results. There was no doubt that Colin met criteria for an educational diagnosis of autism.
Just filling out that screening tool was not enough Bc Colin is smart and was able to use echolalia to seem social.
My son's autism has created a lot of behavioral challenges as well, while academically he is at or above grade level.
With that educational diagnosis in hand we chose to have him placed in a special education school with reverse inclusion, they also suggested he could go in a typical classroom with special supports but we did not feel it was appropriate. He also received OT and speech in school as well as privately and the educational DC has also made respite services available to us. He has really thrived! We expect that we will move him into an inclusion setting in another year.
ABA can help you with the problems you are having with hygiene and meltdowns. Your doctor can order ABA but I would also be trying to get what you can from the school. Be sure to put everything in Writing with them. In our state they have 60 calendar days to get it done. You should have seen our district scramble after I informed them that the CARS was not sufficient and I still wanted the ADOS!
I'm still angry with them. We missed a whole year messing with early intervention when he could have been in a full time program with speech and OT services.
Good luck to you!

In our experience and in many reports from other parents, schools can be pretty unhelpful for kids whose main problem is social (with no academic or misbehavior concerns). Even if they want to help and have the money, they may not really have anyone who knows how to effectively assist with social struggles. Also the school may be set up in a way that doesn't facilitate social practice (for example, only a very short lunch and recess).

It can't hurt to go through the IEP process but it may be frustrating and you may need to figure out your own solutions for "social coaching" for your daughter. Social skills group, local autism family meetups, extracurricular stuff like scouts, private therapists, etc.

Schools are more likely to be helpful with straightforward speech or occupational therapy, for example speech articulation practice.

Definitely push for an IEP - the earlier intervention the better. The IEP changes nothing in her day to day learning other than give her the extra help when and if she needs it. If your school pushes back you can go to the district office. An advocate would be a wise investment if you can do that. Our guy is 10 and was diagnosed with HFA just a year ago. But he also has ADHD and Anxiety Disorder as well as some learning difficulties although he is very bright, and has had an IEP since kindergarten.