From BBC News:

A Sheffield head teacher has resigned after parents complained about her plans to scrap separate assemblies for Muslim pupils. Julia Robinson had wanted to hold one assembly for pupils of all faiths at Meersbrook Bank Primary School.   ...The legal requirements for schools to hold a "daily act of worship" vary around the UK. In an English community school like Meersbrook, the requirement is for "a single act of worship for all pupils or separate acts of worship for pupils in different age groups or in different school groups" - meaning the sort of groups in which they are normally taught, not religious groups. Most acts of worship have to be "wholly or mainly of a broadly Christian character" though others can reflect pupils' family backgrounds. This basic requirement was established in the 1944 Education Act and has been re-enacted in more recent legislation relating to schools.  Parents have the right to withdraw their children from collective worship.