I did a PGCE and my lessons are always either good or outstanding. Your practice develops with time and I don't agree that longer spent at university would help this. Ultimately, you need to be trusted to teach your own classes and schools would not allow students to do this. They would also remain cautious about allowing them to teach exam classes, which is obviously an important part of their development as a teacher.
The biggest issue in teaching remains poor leadership. Bad teachers are often used as scapegoats for wider issues. If you look at any Ofsted report where a school is failing, the teaching may be satisfactory or poor, but there are many, many other areas, including leadership, that will be poor too. Everything needs to function as a whole. I'm not saying don't get rid of people who aren't doing their jobs properly, but doing this will not be the magic pill that improves education.
Posters have said about failing schools where a new Head has arrived, sacked a couple of teachers, and suddenly the school is hugely improved. This is not because the poor teachers were holding it back (how can a couple of people hold back an entire school??), this is because the last Head was rubbish and the new Head obviously isn't. Poor schools inevitably have weak leadership and this is why many 'Trusts' or groups of schools are being formed: to share good practice and to raise standards. It needs time though, but IME is working very well indeed. Teachers are being allowed to set the path rather than local government.
I trained in a school that only had an acting Head. A new Head started and the school went from being a sink school to one of the best in the area in 5 years. He didn't sack any teachers.