Florence, from what you've said, I can see lots of negatives for your son to live with his dad, but not many positives aside from the fact that your son wants it because it will be easier, less disciplined, and more "fun".
What is your legal custody situation? Are you required to offer this, or is the arrangement now following the court guidelines?
From my experience raising two kids of my own and three step-kids, teenagers want what they want when they want it, just because. It's not a time where parents who are effective parents can necessarily be good friends with their kids.
When my daughter was 14 going on 27, she had a great crush on the newly arrived juvenile delinquent in her classroom. She announced at 10 PM one evening that she was going to meet "JD" at the park right then in the dark. I said no. She said yes. I said no, then absolutely no, then h*ll no, then over my dead body. It was quite a performance on her part - she had just had the lead Maria in Sound of Music and really had quite a flair for the dramatic.
It was like playing tug of war with a rope, each of us pulling as hard as we could in opposite directions.
All of a sudden she said "OK." I fell flat on the floor, metaphorically, having girded my loins and suited up in my spikiest armor and prepared for terminal battle.
In bemusement, I said: "What happened that you changed your mind?"
She said "Oh I never really wanted to go, I just wanted to see if you would stop me."
Kids expect limits; they expect their parents to have good judgement and require them to do what they should be doing. They see their job as demanding exactly what they want, and then settling for what they get. It, I think, is a part of the self-definition process a young adolescent is going through where they need to cry out for their independence, yet inside they know they aren't quite ready. And they get their grand tantrum, which pleases them, they get to storm and lightning. They get to try out their wildest dreams but they know they are safe because you are their safety net.
Later, they internalize those limits that you are providing and can make these decisions with internal dialogue within themselves. But young adolescents can't quite get there.
So, if it were me, unless there are court requirements that demand custody changes, I would say no. Your ex husband does not have much to offer his son - poor schools, criminal element in the neighborhood, unstable relationship, and poor history of parenting.
What you might do is set some conditions that have to be met - by both your son and your ex husband - for more extended visits during school vacation time. Take it one little step at a time.
This is a good time to start discussions with your son about short term pleasure versus long term achievement. The ability to defer immediate gratification and invest the energy and motivation in a longer term success is something that kids this age are ready to learn. You can point out the difference between kids who go to college and kids who don't. The difference between kids who do well in high school and can earn a scholarship and those who can't go because they can't afford it.
The deal is the more reasonable judgment and pattern of achievement the teenager shows, the more they get to participate in the decisions about what happens to them. They do not have custody of their parents; the buck stops with the parent to make good choices.
You may not be popular for a while, but that is ultimately often the badge of honor for a parent who has lived through their child's adolescence.
ShootingStar1