'Mild autism'

Hi, my son was diagnosed last week with the above. He is 3.5 and due to start school next September. Although I've been fighting for this, still feel really sad about it, especially as he has come on so much in the last 6 months!  It's a lot to get your head around, felt as if I was told, given a leaflet and shown the door. Wondered if anyone else has had the same diagnosis and how it affected them, their child and especially mainstream school life...thanks for reading, any support would be greatly appreciated :)