OJ, sadly your experience is very common.
I teach primary and always feel so angry on behalf of those kids who need extra support but don't get it because they are well behaved. They get to Y2 and you think, ok, despite being given extra support within the classroom, this child is still not accessing the curriculum and needs to be assessed.
But you're lucky if you get 3 appointments with the ed.phyc each year and those chldren get bumped further and further down the list because the 9yr old who screams at his teacher to f off and throws chairs at people takes priority.
Then the E.P needs to see the 11 yr old who cannot control either his aggression or his emotions and gets so worked up at the slightest thing that he bursts into tears, screams and shouts, trashes the place then does a runner.
Then the last visit of the year will be seeing the 5yr old who has started reception only 6mths earlier but has already asked to see his teacher's c*nt and regularly uses explicit sexual language. We (wrongly) jumped to the conclusion he was being abused. Turned out that his mother was in fact working "nights" IYKWIM. He had been listening in.
This is how each year goes, pretty much. There is so, so much social crap to get through before we can even begin to teach some of the kids I come across.
These children quite literally live in a different world from me and my kids.
The bright kids do ok, you struggle to contain the difficult ones and the poor kids who need the support but don't misbehave to get it, just make do. Nobody wins and very few reach their potential. It breaks my heart and often makes me want to throw in the towel.
Ironically, I am a far batter teacher since working in such an environment than I ever was when working in a far more affluent area. I work longer hours (lunch breaks etc) and my lessons are better.
There are, without a doubt, bad teachers out there. Many more are 'not good' teachers either because they no longer enjoy it or they are unable to impart their subject knowledge to good effect.
Likewise, 'bad kids' is too general. Some kids are just lazy, PITA little sods but many, many more have never had a chance.