Struggling to focus on 1 thing atta time

Hey I'm looking for advice on how I can stay focused on 1 thing atta time because at school I struggling to focus because I can hear my teacher, people talking, P.E. happening in the sports field... I got told of for not paying attention and looking out the window because I heard people out there.

It's affecting my work apparently  I think my teacher just hates me tbh woman is an absolute monster lol  

I was diagnosed with asd when I was 5 because I hated being touched and eating different things was upsetting. I didn't make eye contact either still don't eyes make me uneasy.

But focusing and paying attention is so hard I don't know how to improve this.