My daughter struggled (with the amount of people, noise, proximity, demands) in nursery and primary school but we didn’t get a diagnosis until she was 8.
Until then we didn’t know what was wrong and how to help her. At its worst she would refuse to leave the house, was violent and destructive, began to restrict food and couldn’t sleep.
After many battles with the council (she masked in school) we managed to get her a place at a specialist school and life is completely different.
She is doing well academically, has friends, engages in school trips and activities, eats, sleeps and is much happier at home.