Depending on the district, you can get a decent educational diagnosis through the school. Our district is bad at delivering services and making accommodations, but they use ADOS and I had no issues with how they did the educational diagnosis, itself.
I can understand holding off, until there was a problem b/c you really don't know what your kid can do on his own; but once you have trouble, it can spiral downward very fast. You will need to call an IEP meeting and talk about them doing an educational diagnosis, and assistance. Many people on here have found that process to be inadequate and were forced to get a medical diagnosis elsewhere and present it to them. That said, they still have to do their own assessment b/c a medical diagnosis does not necessarily map to what specific adaptations or services he will need.
Also, typically kids on the spectrum will need Speech, even if they are very verbal -- to help with pragmatic language and social nuance related to this. I would heartily recommend that you access that if you think it would be helpful.