By far the biggest threat to the rights of children to have a chance to learn to love music while at school are the budgetary and curriculum pressures that have largely driven out and ground down music in many/most British schools.

If there really are schools which are providing musical teaching which is worth having, and children who are being denied access to this because of the way their parents misunderstand and misapply their religion, that is a shame.

But I would suspect that the number of children denied access to music in this way is only a fraction of those for whom taking part in religious services is the main place where they have any real access to live and participatory music.