M.G.
C.,
I am a teacher and work with many students either with autism or on the spectrum, including a student this year in the process of being diagnosed in fourth grade. My first recommendation is to either start with your pediatrician or a child psychologist. While I completely trust the school's diagnosis, you still want a doctor to diagnose your child, and then they can direct you toward therapies that will help. There are many things that can be done to help a child on the spectrum, especially with developing social skills.
Good luck! I'm sure it's a lot to take in right now.