Debating coursework. need ideas!!

im doin this debate for my english coursework. and I have to debate against a compulsary prison sentence for underage people carrying a knife. does anyone have any in depth ideas of what I can say?

Well you could expand these key points:

*Lots of underage kids carry knives as they don't feel safe or feel threatened- do they really have to be punished for trying to protect thmeselves?
*Prisons are already really full- almost to the point of bursting- is adding underage kids who have only really carried a knife economical and neccessary?
*We will never actually find all the underage people who carry a knife. No matter how many we lock up, there will still be others out there carrying knives.
*A compulsory prison sentence would require a trial and solicitor. Many people don't have the money to pay for such things.
*Not all underage people carry a knife with the intention to hurt others. As in point one, they carry one to protect themselves.
*The police should be worrying about other crimes that have actually happened.

These are just the ones off the top of my head. Hope they help!