Masking 4 Year Old

Hi everyone,

I have a extremely strong suspicion my 4 year old is autistic, he seen a community paediatrician yesterday who said because he doesn't show behaviours at school, she's just putting his behaviour down to "challenging behaviour " because I have 5 children and he was a lockdown baby, I very much disagree but I have no hope of getting the school ALNCO to help me because she seems to think 4 year olds cannot mask at school.

Can anyone point me in the direction of any credible source that says otherwise? Thankyou!