It may suprise you to know that baptised Sikhs in this country carry ceremonial kirpans. As Jai said though these are nonfunctional. A little education for the reactionary bigots:
1) Sikhism was created about 500 years ago. It was a warrior 'tribe' put together to defend 'India' from invading MUSLIM armies that wanted all Indians to convert to Islam
2) Sikhs have a military reputation and hence formed a large part of the army that helped defeat the Nazis. They fought on all fronts, Africa, Burma, Europe etc. Indeed at least one Victoria Cross has been awarded to a Sikh.
3) Despite this background we are a peaceful people. Unlike Christians/Muslims we have NEVER tried to force people to accept our beliefs. Unlike Christianity/Islam we do not think non believers will burn in hell etc
Wearing a kirpan is an essential part of being a baptised Sikh, even though now it is just symbolic. It is not the same as carrying semtex, bowie knives and whatever other nonsense was mentioned. Sikhs have carried them in western countries for the last 50 years without any bother.
Should this kid be allowed to carry a real functioning knive to school? Of course not. A symbolic, sealed or blunted one yes.Thing is you will not see 100000 sikhs across the world marching or rioting to support his right, because that is not the way we behave
Sikhs have integrated and embraced their host nations. We do not hate western values( especially not the drinking bit!)
Just because there are some sections of the community out there taking the piss don't label all of us. Sikhism is a peaceful, embracing, modern and non judgemental way of life.