But wouldn't the ending of sibling policies have the potential to have a negative impact on low income families?
Consider the case of a low-income family renting. The oldest child is awarded a place at school X. Imagine the family has 3 children. The younger children are likely to be attending a local school. The family's lease expires as second child is coming up for secondary transfer. The family have to move, perhaps just out of catchment for the school child 1 attends. The sibling policy isn't in existence, so they are faced with the prospect of 3 children at three different schools, all some distance from each other. The logistics of that are a bit of a nightmare, given that the family are going to have a struggle paying transport costs.
Which children will they move, from which schools? Would you want to move child 1 in, perhaps, a GCSE year, given that the options that child might be studying may not be available elsewhere?
And not all families, as other posters have pointed out, live where a variety of schools are an option - the schools might be literally miles apart.
I agree that the whole renting-for-a-year to get all your children into a school, either primary or secondary, phenomenon - is incredibly frustrating but I do think that the other options are really hard on those renting, or forced to move for a variety of reasons (illness/death/sudden loss of income/divorce).