Why assume it's the teenagers who are doing this? My sister was nicking stuff age seven onwards. It was bloody annoying as, when we grew older, my mother refused to let me have any locks - and TBH although I did buy a box with a padlock why should I keep ALL my money, my make-up, my good pens, my favourite books etc under lock and key hidden at the back of a wardrobe? And we BOTH got the lecture, even though it was known it was my sister, because we couldn't be treated differently. Why not, we acted differently!

She hasn't done for about a year, as far as I know, but if you ever buy yourself a treat and leave it lying - oh, I don't know, in a drawer in the bedroom - it will be half-gone the next week. So glad I moved out!

Anyway, just saying that it may be another of your children, don't blame teenagers automatically.