If you want your children to keep the faith - don't send them to a Catholic school!

Not my words but those of Archbishop Sheen, uttered, I guess, in the mid seventies, a year or two before his death.
He went on to explain that, at a Catholic School they would probably receive a bland sort of grounding in the faith but that, if they went to a non Catholic School, they would have to stick up for their faith and become stronger and more knowledgeable as a result.
There are a few, very few, good Catholic Schools in Great Britain today, Cardinal Vaughan is one; the vast majority fall into the mindless liberal category. Archbishop Sheen's advice is sound overall,  except that, today I would add a caveat. Send your child to a non Catholic School only if both parents are strong Catholics. Children need the primary ethos of Catholicism to come from the home. Then they can stand up to the barracking they will receive at a non Catholic School.
If the home faith element is not so strong then, at least a Catholic School will give a base to be built on and, equally importantly, a network of Catholic friends.
As parents we had very bad experiences of our local Catholic Convent School. By the age of eleven, most, if not all of the school children knew nothing about the Sacraments or transubstantiation. They did know how to colour in pictures of the parables and stick them up round the walls.

All too often, RE becomes an art class rather than an instruction in catechetics

Sadly, the worst influences can come from embittered or disenfranchised Catholics, either teachers, family members or friends. And if one of the Catholic parents is weak or ignorant in the faith, it can cause friction and even apostasy. Couple this with a wishy washy school experience and you have young men and women who, in all probability, may never go to Church again in their lives and whose salvation, as a result is in grave doubt.