I'm sure there are other organisations out there who wish their percentage of incompetent staff was this low.
The job itself tends to weed out those who can't hack it and they go elsewhere where they (hopefully) can.
We all know teachers with learning responsibilities that they neglect, clock watchers and snobs that think only the bright need a proper education. I would love to make sacking teachers much easier.
A few people in teaching are not suited to it and should not have been passed on their PGCE.