Teacher-trainers in England are producing the best-ever generation of new professionals, according to inspectors.
But the standard of training run by schools still lags behind that run by, or with the help of, universities.
David Bell, the chief inspector, this week gave a preview of the Office for Standards in Education's report on the past four years of inspections of initial primary and secondary teacher training.
He welcomed the significant improvements in all aspects of training. His preview says that:
* training was good or better on around 90 per cent of primary English and maths courses, and 80 per cent of secondary subject courses.
* trainees' teaching skills were good or better on almost 90 per cent of primary and secondary courses.
* unsuitable trainees were very rarely recommended for qualified teacher status because trainers had become better at assessing them.
* primary trainees' English and maths knowledge had improved considerably, partly because of the national literacy and numeracy strategies.
Trainees were still weak in some areas, Mr Bell said. In particular, their abilities to assess and record pupils' progress was not good enough - reflecting the weakness in this area in schools where they trained, said Mr Bell.
Also, secondary trainees lacked an understanding of the primary curriculum and vice versa. This was a key issue to be addressed given the decline in pupils' performance when they transfer at age 11.
On-the-job training courses continue to perform less well than university-based partnerships. Few school-based initial training courses produced very good trainees or had very good training, and a higher proportion had significant weaknesses.
Schools sometimes underestimated what was required to train new colleagues properly, said Mr Bell: "It is absolutely right that schools are at the heart of the teacher training process. But it's very difficult for any school to go it absolutely alone and provide high quality training.
"Almost all the best provision we saw was where schools worked collaboratively with other partners, usually universities. That was true whether the initiative for the partnership came from the school or the other body."
Jim Hudson, chair of the National Association of School Based Teacher Trainers, said: "I would have preferred it if Ofsted had been able to say the school-based initital routes were better, but we want to get better."
* The average trainee teacher now spends half of their time in school, says Ralph Tabberer, chief executive of the Teacher Training Agency. The rise in time spent in school, rather than at college, is the result of the expansion of on-the-job training, particularly the Graduate Teacher Programme, and could rise further.