???This child is 13 years old, his mother must be able to demonstrate care, control and responsibility for her child. She must provide for his welfare and meet his needs as a loving and responsible parent or she will find that the law will step in and she could lose thise parental rights.
As an educator of secondary school age children, a parent of boys...DS2 an educator himself you must take action. Years ago DS2 did a bit of experimenting himself and grew a couple of plants, fortunately it stayed at that an experiment. He was 16yrs then, but the suicide of one of his friends who did not stop there some 4yrs later has given him deep emotions concerning drug use. His FB account hangs, 14 years later.
There are no half measures here. You have a 13 year old child who is scared, out of his depth, unhappy, confused and worried. You have a situation far more concerning than him sharing spliffs up the recreation ground.
You need to keep him home. You need to carefully coax out of him where he is going, who with and when he gets these drugs. How he is buying them and how he pays for them.
You need to control his access to social media. Take his smartphone and replace the SIM card with a non internet package or give him a basic phone. Set controls on the computer so you can access it and his accounts. Hes barely old enough to use social media! You then need to take him to see counsellors, speak to FRANK who will guide you and put you on a pathway,. You could try the GP, select carefully if its a group practice. Others who could get involved may be his school..who may already be aware that he is going offrail with drugs or behaviour, social services and the police. Since the latter two have powers of intervention, you dont want a situation that they knock your door before you have a chance of sorting this.
He really is on a slippery slope and you must be very proactive, you need to keep the communication door open. Hopefully he has had a fright but the fact that he is asking you to let him out to smoke weed means that he will reconnect with the people he has been running with. You must stand firm and importantly set boundaries. It does sound that you may not have done this. You must get help before the problem worsens. He could get involved with county lines..distribution in return for his drugs, violence, bigger criminals and crime. You need to stand firm, get support and work through this, dont give an inch where drugs are concerned and your child is a little boy. He might think hes streetwise but he is not old enough to understand damage limitation. Zero tolerance. Good luck.