Universities continue to provide the best teacher training in England, according to the latest league tables.
But there is evidence that big providers are losing ground to smaller specialist institutions, particularly in converting trainees into qualified teachers.
The tables also show that some subject areas can recruit only graduates with poorer degrees. Those with firsts and upper seconds continue to shun teaching for more lucrative careers elsewhere.
Oxford University, which the league tables ranked number one overall and best for preparing students to teach in secondary schools, is a model of an emerging "smaller is beautiful" factor.
Despite leading the field for the past five years, Oxford has continued to limit its intake, helping to maintain high quality and a healthy proportion of trainees finding jobs in teaching.
Staffordshire University, which has the smallest intake for a university and specialises in training students to teach business studies and economics, is ranked second in the overall and secondary league tables.
Meanwhile, a merger of teacher training between Homerton College, Cambridge, and Cambridge University, appears to have caused Homerton to drop in the overall rankings from second to 20th place, and Cambridge to fall from 11th to 29th place.
The tables are based on Teacher Training Agency data on the entry qualifications of teacher training students, the quality of provision and the proportion of trainees entering teaching.
Alan Smithers, director of the Centre for Education and Employment Research at Liverpool University, who analysed the data and compiled the tables with colleague Pamela Robinson, said it appeared there could be an "optimal size" for teacher training providers.
He said: "The overall balance of provision needs to be looked at. The small-scale schemes that are highly specialised can do very wellI (they) can also be subject to a greater level of variability. It would appear there may be an optimal size that providers should seek to maintain, which is what Oxford has done."
The University of East Anglia holds third place in the overall table, followed by the University of Warwick. Two school-based schemes, Bromley Schools' Collegiate and Outstanding Primary Schools SCITT, come fifth and sixth.
The top three primary teacher training providers are UEA, Warwick and Homerton, while Oxford, Staffordshire and Warwick top the secondary table.
Data on qualifications held by entrants to teacher training show the difficulty of recruiting good candidates for some specialist subject areas. Among postgraduate entrants in maths and modern foreign languages, barely a third held a 2.1 class degree or better, compared with over 50 per cent of all graduates in these subjects.
Better qualified postgraduate trainees could be found in drama, where 64 per cent of entrants held a 2.1 or better compared with 59 per cent of all graduates; physical education, with 50 per cent good degrees against 34 per cent of graduates; and social sciences, with 61 per cent good degrees against 53 per cent.
Full tables available to subscribers here