My grandsons behaviour

[Herbyl]

I am trying to help my daughter get information to help her 5 year old son. Her boys are twin IVF babies (not that this should have any relevance), the oldest of the two is having behavioural problems. His school is trying to help, but it doesn’t appear to be succeeding. He cannot stand loud noises close to him, he runs away when he hears the Hoover, his speech comes in dribs and drabs especially when he is excited and wants to tell you something. The school says his number work is good, his reading is good. But when you tell him NO he then lashes out to the point he punched his helper at school. On the other side he can be so loving.

Can anyone please help/advise?