In many secondary schools, much of the work that used to be carried out by year heads, such as dealing with attendance, behaviour and pupils'
families, had been passed on to support staff.
"In challenging schools this transfer of responsibilities has improved teachers' morale as dealing with disruptive behaviour on a daily basis was time-consuming and dispiriting," the report said. However, secondary schools were not as good as primaries at making use of assistants'
individual experiences and skills in lessons, tending to leave them to work with pupils with special needs.
In schools where staff had not been properly consulted about changes to the workforce, a minority of teachers felt resentment towards their non-teaching colleagues. Teaching assistants also said that in some schools there was confusion over their roles, status and pay.
After 15 years as a hairdresser, Trudy Williams, 46, became a teaching assistant in 2000 at Hillcrest school and community college in Dudley in the West Midlands.
For the first 18 months in the job, she worked 25 hours a week helping one special needs pupil with his learning. This involved preparing teaching aids for him and assisting him in the classroom on a one-to-one basis.
In 2002 her role began to change, and Ms Williams was given administrative tasks, including preparing individual education plans for several pupils, while liaising with teachers.
Now she is also in charge of inductions for Year 7 pupils who start at the school other than in September, as well as any pupils who do not speak English as a first language.
"I make sure they are fully integrated and settled well into the school, which could involve looking at appropriate teaching groups, finding other children with the same language and other areas of support.
"I did enjoy the job I used to do, but I enjoy the role I am doing now much more," she said.
"It is a totally different job, and the teachers love it too that we can take on all these extra roles. It is much more diverse. It is very, very busy, but I love every minute of it and still spend a lot of my time in the classroom supporting in all aspects of teaching and learning."
She has also written a guide for parents outlining how to cope with an autistic child. Next year she will be in charge of a team of 15 support staff.
Ms Williams was named teaching assistant of the year at the first national awards ceremony for school support staff last month.