My Autistic Son Pushing

Hi, im looking for some advice and guidance for my son. He is 4 years old, and just been diagnosed with stage 2 autism. His new thing at the moment his having meltdowns at home,then pushing children at school. As today he pushed a child and they hit there head.

As a mum, me and my partner are struggling as we aren't getting much help. As this is all new to us. So any advice would be helpful. Thank you.