The overwhelming majority are women in their 30s and 40s, mothers themselves, who often start out as unpaid volunteer parent assistants, and usually learn their role `on the job'.The work is poorly paid, generally insecure and there is no career ladder to climb.
What they do varies from school to school. Mundane but necessary tasks such as preparing teaching materials, tidying away classroom equipment, helping children tie their shoelaces and so on, are part of the role, but increasingly classroom assistants are playing an important part in children's learning. They can be found reading with children, marking and commenting on their work, assessing and recording their progress and even organising activities.
Generally little noticed by the educational establishment, it was the increased pressure generated by the National Curriculum that brought their role into greater prominence.
The first national pilot scheme for the training of `specialist teacher assistants', was launched in 1994. From the beginning the Open University was the largest single provider of training, with 300 students in 10 local education authorities (LEAs) taking part in the first year. This year there are more than 400 students in 20 LEAs in the OU scheme.
The course is demanding. As well as supporting the children's learning of English, maths and science and becoming familar with the detail of the curriculum content, the students also look at how schools are organised, curriculum planning and the assessment and recording of children's progress.
Training occurs both at work and in the assistants' own time - the University's estimate is 270 hours of home study on distance learning materials, and 150 hours in school carrying out specified tasks and a project, during the course.
The educational requirements for admission are not high - passes in GCSE English and Maths or equivalent- and many of the assistants have been out of formal study for a long time. The level of commitment and ability demonstrated by this, previously undervalued, group, has impressed the university's course team.
The University has worked closely with teachers' organisations to allay fears of a backdoor attempt to replace skilled teachers with a cheaper alternative.
"Teachers now realise that a better-trained classroom assistant is a more effective part ot the team," says Will Swann, who has run the OU's STA course from its beginning.
"And we now have evidence from our surveys that head teachers value their competence."