Teenagers eh?
This is the wonderful age when they seem to have forgotten everything you‘ve painstakingly achieved over the last months!!
I would suggest the long lead and always with a long lead, a good fitting harness.
You‘ll probably hate it,
especially now he’s running free and you‘ll feel mean
but its honestly worth sticking it out for a couple of months, it‘ll pay out in the end.
Try and start somewhere where the distraction level is relatively low if you can, let him sniff and wander, every single time he looks up or back at you, praise him - you can throw a treat towards him occasionally. The aim is that he‘ll learn a sense of the distance he‘s allowed to go and will encourage him to keep checking in on you! You can recall him now and again and reward with a game or treat or whatever, but don‘t overdo that either, a couple of times on a walk is enough.
Its a good idea to start teaching some impulse control at the same time, get him to sit and stay while you throw the ball (within the range of the lead) and then release him to fetch it. Also teaching a stay while you walk a few steps away from him will help his self control. Another useful thing to teach while on the long lead is a STOP (as opposed to a recall).
I swore and complained a lot when I started with the long lead and lost count of the times I nearly tripped over it but, we stuck to it for about 3 months and, although we live in the middle of the country and he‘s off lead most of the time, he‘s very rarely more than about 10 meters in front or behind me.
Hope that helps, Best of luck!