Ask the school whether the children are all on the same register or not?
I have known schools to have two separate registers - one is nominally allocated to the non-teaching Deputy Head.
The two classes are then combined on a day to day basis and taught by one teacher and two teaching assistants.
This is a sneaky way of sticking to the rules (sort of, by maintaining two registers), but saving money, by only having 1 teacher.
The trouble is that schools need 28 (I think) pupils in a class in order for the class to "break even", financially.
Schools which have an intake number of either less than 30, or between 30 and 60 have a real problem when it comes to balancing the books as they generally run each class at a loss (unless they mix classes to make a total of 30 children in each class).