Jessica,
What you need to do is emphasize the science behind food allergies and sensitivities with regards to ASD and ADHD. Don’t talk about diet being a cure, but how food problems are a known co-morbid problem of ASD/ADHD. You will have to do some research, but just start pulling up research abstracts on things like – gluten and autism, food allergies and ADHD. There is a ton of stuff to be found that would back up your position. Research the Centers for Disease Control website, as well as the National Institute of Health. There is some research out of Europe:
Medical Comorbidities in
Autism Spectrum Disorders
A Primer for Health Care
Professionals and Policy Makers
Second Edition: July 2014
These are all standard and conventional agencies. What this will do is make the statement that diet does matter and if it matters to the CDC, NIH, than it should matter to the parents. This will leave the school director with nothing to counter because you are presenting overwhelming conventional scientific research.
Dr. Woeller