My DD had similar in year 3, she suddenly hated school, was biting her nails, but wouldn’t say what the matter was. One of her friends broke down in tears and told her mum that another child was bullying mine.
I spoke with the school and the child was moved away, but I am disappointed that it took another child to identify the problem, that the teacher didn’t see it, after 5 months! That said, the next child lasted 3 weeks sat with the child and the next one only 2.
I promised DD she would never have to sit with her again, I tell the new class teacher each year and when the seating plan puts them together I am on it immediately and remind the school how they allowed the child to bully mine for 5 months and they are not allowed to be together.
School have maintained the separation, but only because I make them.
Secondary school soon, the child has put our first choice school as their first choice, but we are higher up the admissions categories than they are, and to my knowledge no places have been given to children that low down the categories in at least the last 4 years, so unless the child has an EHCP the parent has kept quiet about, I am confident we will escape them. If we don’t escape them, I will advise the new school of the historic issues and ask the, to be placed in opposite halves of the school which would massively reduce any chance of shared classes,