Teacher ask for child to be collected from school because he was throwing things

Teacher ask for child to be collected from school because he was throwing things
What support can I access to assist my son, who has been having behaviour issues that have been increasing for 6 weeks? He has been vocally matching other children in the class (it is important to add that my son is verbal, and the other children are non-verbal, as in they do not communicate using words, but I guess they communicate both using their device and vocally). My son will continually be vocal and disturb the class, hit the teacher, hit other children, throw things at the assistant teachers and other children. He has an autism diagnosis (level 3) and has been attending the education support classes at the same school for 5 years without any behavioural issues until recently.
The first 4 weeks, this behaviour was communicated to me by writing in the communication diary, which is kept in his school bag, by speaking with Dad after school during pick-up, and through a behaviour support plan that was sent home for me to sign and return the following day. The strategies included him requesting a break, requesting to go to another class, or the sensory room. If this is done five times, he is rewarded with a treat. During this time, I expressed wanting to meet with them because of the things written in the diary, but his dad, the messenger, let me know they (the teachers) said this was not necessary because they thought they could deal with it, and the strategies they were using were helping.
Last week, I requested a meeting in writing via email, and we met later in the week. I said I was concerned about the things written in the diary and was not sure why no one had called to let me know at the time of the incidents. I also wanted to follow the same strategies at home but had some issues because of different parenting styles between me and Dad. We will meet again tomorrow with both parents and his therapist in attendance. He was excluded from school today because they were unable to stop him from throwing things at other children, and he was placed in a class by himself. I understand it is a safety concern, but what services can I access? What steps should I take? What can I do as a parent to help my son with his behaviour issues?