To the OP, please be very careful. Marijuana use can open a gateway to use of other, harder, more dangerous and addictive drugs. Lots of kids smoke pot at 13, and lots of them end up in full blown addiction to other drugs within a couple of years.
Not everyone, but lots. Marijuana in itself is not that harmful but the thing is that more often than not, where there is pot other drugs are sure to follow. Kids your age are usually anxious to try new things and a kid that's into pot will probably want to try another drug sooner or later. A kid that's into pot will probably be exposed to other drugs sooner than a kid who doesn't smoke it.
Can you quit whenever you want? Not necessarily. Plenty of people are addicted to marijuana. Not a physical dependence, but a psychological addiction which is very real.
Can you control it? Not necessarily, that's the nature of addiction.
How long til something can happen to you? Maybe nothing will happen to you.But maybe sometime soon you'll be toking and someone will introduce another drug and you'll try it. And you'll like it. And you'll start actively seeking out that other drug to use along with your pot. And things spiral downward from there. Or maybe you'll just start to need the pot itself, and it will become your priority and will interfere with your life in a negative way.
You're smart to ask, and you'd be smart to just say no. It's not easy but it is always the best decision when you're still in middle school.
How are your grades by the way? Have you seen any of your friends who smoke pot getting in trouble because of it? How about other kids you know?
Is it worth doing?
It's illegal , you know. No matter how much fun it is it's not worth getting arrested for.