we don't know what he has told the teacher about the mother but none of it will be true.
Tread carefully
Your relative should make an appointment to see the Headteacher if she has concerns about the way her child is being treated, or is at risk from her father. Presumably he has access to the child as he is in contact with her teacher. Favouring the father' is a very ambiguous statement and she needs to be clear as to what exactly she is implying.
The records from the Nursery should have been passed on, but this does not always happen, and she may certainly ask if this is so, and I believe, request to see them.
To think that London, or anywhere else for that matter, does not belong to any one demographic