If the police have reason to believe your doing something wrong they have the right to ask you what you have and ask you to open/empty any bags or pockets you have. It does'nt matter what your age is.
Just a tip Never Ever carry Wepons of any sort. It is a very serious offence now.
If you do have a run in with the police: Do what they say,
Don't resist or try and argue, It'll just make any problem worse.
Be good, Take care.
Peace