Obviously, I wouldn't have wanted my dd around kids that I perceived to be dangerous in any way, but personally, I was very happy that she was exposed to a wide mix of people, including some that were from very different backgrounds to her own, and some that were being brought up with very different value systems. Through getting to know these kids, she learned to be more self aware, more socially aware, more empathetic, less judgmental etc. All qualities that are very important to me.
I had similar experiences at school. There were a couple of kids in my secondary school, in particular, who probably taught me as much about the world as any of my teachers did.
There was one lad who was constantly in trouble, always getting told off for causing disruption etc. He got blamed for everything even when it wasn't his fault! I am pretty sure that, these days, he would be diagnosed with adhd, but back then, he was just considered to be naughty. I went through the first year or so of school thinking that he was "bad" and steering clear of him as much as possible. In my second year, though, thanks to my timetable and groups for subjects like art and cookery, I ended up getting to know him quite well. He certainly was disruptive, but I also learned that he didn't have an unkind bone in his body - he was actually one of the kindest and most thoughtful person I've ever met, but he just didn't know how to keep himself out of trouble.
The other kid used to sit next to me in maths. I was a bit scared of him for the first few months. He seemed quite "rough" and even the teachers seemed a bit way of him - he could be quite rude to them sometimes and I saw that they barely batted an eyelid. I was bemused by the fact that he sometimes seemed very quick to learn and picked things up without any trouble, whereas at other times, he was completely and utterly disengaged. I was scared to even speak to him at first, but we were sat next to each other in every maths lesson for 2 years, so I gradually got to know him. And I learned that he had spent a while living in a refuge when he, his mum and his sister had escaped from his abusive father, that they had then managed to get a house which his father had tried to burn down with all of them in it. And I realised that he cultivated his scary exterior primarily because he felt that this would give him a better chance of protecting himself, s mum and his little sister from anyone who might want to do them harm.
Those insights into lives that were very different from my own undoubtedly helped to shape the way I see the world now - my values, my politics and even my career in many ways. I am grateful for having had genuine opportunities to step out of my own bubble, and to realise how incredibly easy it is to judge from a position of ignorance.