How do you get Money if your a 11 year old kid

if you enjoy soccer, you can ref for younger kids.

see if your parents will pay you for some extra chores, like mowing the lawn or watering plants or something.
A garage sale! I'm sure you have loads of stuff from when you where young that you don't use any more. Just sell them at a garage sale. If you have lots of stuff then you can afford to sell things cheap. If you have lots of small toys e.g. free toys from fast food resteraunts then tie some up in a small plastic bag and Mae lots of these then sell them.