It does not respect the rights to freedom of religion or belief that our children deserve, and is therefore an abuse. Collective worship forces young people to pray or worship in ways that take no regard of their personal beliefs, or those of their parents who may be further restricted in school choice. This also alienates some who may feel the need to self-exclude, or who are excluded by the beliefs of their parents, and the system where a parent can exclude a child out of religious worship is deeply flawed.
Assemblies are useful for the school community, and this does not and must not include enforced and divisive collective worship. The UK has a plurality of beliefs and these should be recognised and respected.