The Department for Children, Schools and families produced a leaflet.
The Schools, Parents and Parental Responsibility (Ref: DfEE 0092/2000)
guidance:
It states:
"General Principles for Schools
Everyone who is a parent, whether they are a resident or non-resident
parent, has the same right to participate in decisions about a child's
education and receive information about the child. However for day to
day purposes, the school's main contact is likely to be the parent with
whom the child lives on school days.
School and LEA staff must treat all parents equally, unless there is a
court order limiting an individual's exercise of parental responsibility.
Individuals who have parental responsibility for, or care of, a child have
the same rights as natural parents. "
So unless there is a court order stating a parent cannot collect a child from school, the school must treat both parents equally, meaning they cannot stop a person with PR collecting their own child from the school.