The Office for Standards in Education says that assistants now spend more time on learning support, leaving teachers to do their traditional tasks, such as preparing materials.

“This shift means that teachers have to do more welfare and administrative work that could be done more appropriately by teaching assistants,” says the inspectors’ report.

Teachers told inspectors that having an assistant requires them to spend more time on planning and preparation. However, “they regard this as worthwhile because the teaching assistant helps create a better working atmosphere and hence makes teaching less stressful”.

Chief inspector Mike Tomlinson said: “As yet, the considerable public investment in expanding their (assistants’) numbers has not led to a reduction in teachers’ workloads.”

The report also gives clear evidence that classroom assistants help learning.

“Observable gains in a pupil’s learning often result from the individual attention of the teaching assistant in a particular lesson,” it says.

In particular, they are making a valuable contribution to the teaching of literacy and numeracy.

“The evidence from inspection, that the presence of a teaching assistant in the classroom improves the quality of teaching, is very encouraging.”

“Teaching Assistants in Primary Schools: An evaluation of the quality and impact of their work” can be viewed at www.ofsted.gov.ukpublicdocs02teachassist.pdf