Helping a parent come to terms with having a child with autism?

I'm working with a parent of kindergartner who I'd bet has autism. The school secretary even stated it when they came to register over the summer. He's receiving special education and speech (he carry on a basic conversation), but there's a lot more I could get for him with a diagnosis of autism from several different sources. He's having major outbursts because of the lack of visual aids, etc. My small school only has 30 kids with disabilities and most are LD, of course. Anyways, mom refuses to take him to a doctor, for even check-ups, because she doesn't want him diagnosed with autism. (Yes! She actually said that!!) I don't know how to say or what to say to help move her past that. I really do want what is best for her son and give him the kind of resources that will help him the most. He's quickly going to force a move to a behavior cl because of lack of cooperation.