Swearing - 7 and 8 year olds

[BatmanLovesRobin]

Twice now after school club have told me my 2 DSs have sworn ('crap' - which I suspect comes from DH and 'bloody hell' - which comes from Ron Weasley).
The first time I told them off and stopped pocket money (£1) for that week. It obviously didn't work, so last week I told them off (sad, disappointed, embarrassed - that kind of telling off) and banned them from the computer for the week. Later on, I caught DS2 banging his head and saying 'shit' (which has come from school - I am a teacher and am massively conscious about swearing in front of children).
I don't know where to go next - what do I do to make him / them see it is unacceptable to use bad language?

My approach has been to explain that some words you can say to granny and teachers, others are to be reserved for close friends and private thoughts only:) If in doubt, keep quiet or check with parent before using... Having grown up in a household with zero swearing and hence looking like a nerdy choirgirl in verbal fights for many years, I think a reasonable stash of profanities are not a bad thing.

Haha - me too! Didn't swear until I was 13 - but picked it up fairly quickly at my new secondary school in Essex

Thanks - I'll try not to get too stressy about it.