Little brother smoked weed?

Sorry to say it but you need to tell on him because hes too easily influenced. What his friends start smoking crack? Is he gonna do that too? Something to think about.

its not that big of a deal

I would talk with my parents if it happened to me - I don't think there's any point in "punishing" your brother for what he did in the past, but it's important he knows that people know and they'll be keeping an eye on him and he shouldn't do it in the future. At least until he's old enough and in a place where it's legal.

Dont keep this a secret tell your parents if you let him keep doing this then hes only going to hurt his body with drugs and later he will probably go and end up being a huge wreck in his life make a stop to this

If you're concerned about health issues there's not much to worry about. Literally no one has ever died from smoking too much weed and it's not addicting and you can still function with daily life while being high. Basically smoking cigarettes and drinking alchohol is a million times worse than weed so his health is not to be worried about I believe.

In terms of studies as long as he's not high all day he'll be fine. I guess it'll be a distraction but if he's just smoking over the weekend in his free time it's ok. Just make sure he doesn't make it a habit. If you scold him he probably won't let you know about anything anymore so don't, lightly ask him here and there about it just to keep track in case. If he's doing it way too much on a pot head level then you should interfere but I don't think you should get your parents involved right away cause as you said he'll end up trying to sneak it. Obviously if it continues to be a problem you should let them know nonetheless.

Think of why he told you? Was it an outcry for help? Was it asking for advice? React accordingly. I would say encourage him to do some sport or a club. Maybe hang out with him more and be a great role model. The longer time he spends away from those friends, the less influence they will have. Trust me i smoked weed in middle school and some in high school but that was only because i didn't have anyone else to hang out with. So i stayed with the crowd. If you can get him away from them and get him doing some positive things either with another group (like chess club,mma,auto tech class, football/soccer) his mentality will change. Or if he meets a girl that school focused maybe she will motivate him to do his work and get away from his friends? Its not your brother its his environment. Humans adapt well to new situations. If you change the environment he will change too. Just try to leave forcing things as a last resort. If he doesn't budge then tell your parents. You tried to resolve the issue the easiest way possible. You don't want him to end up like that then do it the hard way.

It's rough on a teenager to do this. It usually interferes with studying and doing disciplined things like football practice and math. People tend to do whatever pleases them, which may not be so bad. Adverse health effects are very few, if any.