s'enculer means to f*** yourself or b***** yourself - a general term of insult rather than a specific order to so domething physically impossible. Dundurn's translation is as good as any.
Yes dead right - it's the sort of thing Y8's would ask the teacher because a Y11 had told them it meant something rude - normally the teacher has a get out - in that either the pronunciation or the spelling (as in this case) is wrong!
RG - 30 years of answering such questions later .......