Hands up all those who've never had a CRB check. I bet there aren't many of you. My husband, who is what used to be called a lay reader in the C of E, has just been told he has to have a new one (presumably so that they can take into account all the abuse he's carried out since the last one). I've had to have at least two, the last one in order to be able to teach creative writing to a class of adults. I would have thought that I was in more danger than they were (there were more of them, for a start).
But I know something about paedophiles. I have come across some, and have had many clients who were sexually abused, and in none of these cases would a CRB have helped in the slightest. A young single mother I know discovered to her horror that her son - then four-and-a-half - had been systematically and severely sexually abused for a year by his father, who at the time had regular access. But the child's (very graphic) evidence couldn't be used in evidence against the perpetrator because of his very young age, although everyone, from his teacher to his GP, believed him. So while there is a restraining order against the father, he is still out there. He has a new girlfriend. With small children.
But never mind. You can rest assured that the kind lollipop lady who is helping your child across the road has had a check, as have all his teachers, and the nice woman who teaches him the piano.
I bet that's a weight off your mind.