You are entitled to remove your child from RE.   The RE that was taught to my daughter was almost completely christianity based and she spent much of her time arguing with the teacher about what was fact and what was not.   This was not at a religious school. So we just took her out of the class and at that point she did her violin lesson and helped the music teacher in class.

Anoyingly for her - it had to be our decision and not hers.

We did not opt out of asemblies which we also entitled to do as that would have separated her from the class too much and at least some school info was given amoung the hyms and prayers.

J