By Angela Harrison
BBC News, education and family
Such software can protect teachers and pupils alike, say supporters
Teaching unions are complaining that e-safety software is increasingly being used to keep track of their members.
They say thousands of teachers are having their every mouse-click monitored, eroding trust.
So-called spyware has increasingly been adopted by schools to tackle cyber-bullying and to stop pupils accessing unsuitable websites.
Such software can record online activity by individuals, including web pages visited and messages sent.
Leader of the NASUWT teachers' union Chris Keates says monitoring of teachers' computer use is common - and a symptom of "a growing culture of surveillance".
She said: "I think it is more widespread than we realise. There is surveillance of teachers in classrooms for all sorts of things.
"There is the big issue of CCTV in classrooms and two-way mirrors.
"I think laptop surveillance is being used to see how teachers are using their time, checking that they are not logging on to Facebook or looking at the internet for something personal."
Ms Keates added: "It's about professional trust and confidence. Teachers have more restrictions than their pupils these days".
The other big classroom teachers' union, the NUT, has also said it is "very concerned" about the use of spyware. It plans to send guidance to members.
Telford and Wrekin Council in the English Midlands is one of the many local authorities understood to have introduced such software in all its schools.
The council says everyone who logs onto system sees a screen which says activity on the schools' computers is being monitored.
Richard Lawson, ICT strategy manager for children's services at the council, said such software helped to protect teachers and children alike.
"We have had this for three years or more now and I have heard teachers say it is the best thing we have had," he said.
"It picks up all the cyber-bullying, which is a huge issue for children."
He said such systems offered protection for teachers in cases where false allegations were made against them or where they were being bullied.
The agency charged by the government with promoting good use of technology in schools, Becta, says schools should take a "responsible approach to monitoring".
Stephen Lucey, Becta's executive director for strategic technologies said: "Monitoring software should be used to help keep school computers and everyone that uses them safe, not to spy on teachers.
"Becta advises all schools to maintain a clear acceptable use policy for all network users, so that they are clear about what is considered acceptable and understand the consequences if policies are breached.
"At the same time, it is important that head teachers take a responsible approach to monitoring and use the software appropriately. Our advice has always stressed the importance of ensuring that if monitoring software is in place, all users are made aware of it."