Thats nothing to be ashamed of Lesley, its perfectly natural to feel that way. Ive been in a few situations, (in my students days - and not at my choosing I might add) where its been fight or walk away. Ive chose the latter every time and the first couple of occasions I used to think I should of done something there...... But I soon realised its not about that..... Taking your situation you could of lashed out very easily and where would that of got you? In shit loads of trouble as you quite rightly put!

May we ask what the outcome was? (i.e. is the little bugger facing expulsion?)