Parents now feel they can access teachers 24 hours a day, seven days a week, and have got into the habit of firing off “aggressive and accusatory” emails at any time of the day or night, a teaching conference has heard.

Teachers said that since the outbreak of the pandemic, the parameters of their job had become blurred, and parents now felt they could just “jump on the phone” or go on to social media to directly contact their child’s teacher outside school hours.

Responding, the head of the NASUWT teachers’ union said teachers had the right to “disconnect” at the end of the working day and called for the return of home-school agreements so that parents understand what they can – and cannot – expect from teachers.

Home-school agreements were scrapped in 2016 to try to reduce bureaucracy in schools, but the NASUWT general secretary, Dr Patrick Roach, said schools needed to reset boundaries to manage parental expectations and protect teachers from excessive demands.

Many teachers had been told to download apps such as ClassDojo, which link families and teachers, the annual conference of the NASUWT teachers’ conference heard on Sunday. But while such technology was useful during lockdown to keep in touch with children and families who were learning remotely, teachers now fear they are expected to be available to parents at all times.

Sharon Bishop, a teacher working in Wolverhampton, told delegates the changing relationship between parents and teachers was having a detrimental effect on teachers’ mental health. “Parents of students now feel they can access teachers 24 hours a day, seven days a week,” she said.

The conference was told of teachers being driven to suicide and others being driven out of the job by the pressures involved. “Working hours and parameters have been blurred since the pandemic,” Bishop said. “Parents and students have got into the habit of firing off emails 24/7 with the banal, bizarre and sometimes, more worryingly, aggressive and accusatory messages.”

A Scottish delegate, Kat Lord Watson, who worked in a private school during the first lockdown, described the agonising experience of teaching online, knowing that parents were “watching you and rating you on their WhatsApp groups”.

She has since moved to work in higher education and was given funding to do a small-scale study on the impact of parental complaints on teacher mental health and wellbeing, in which it was claimed that changing channels of communication had made complaints more pervasive and personal.

“The direct line to staff has become much more rapid and the willingness to just jump on to the phone and make a complaint is definitely much more there than it ever has been,” one participant said.

Others who participated in the research reported an increase in unrealistic parental requests. “You just think, really? That’s not something that you could actually ever expect of a school. It’s not reasonable to expect a school to be able to support you in that.”

Speaking to the media after the debate, Roach said some schools were putting pressure on teachers to respond immediately to parental requests, even after hours, saying: “I don’t want parent X rocking up the following morning, saying ‘I emailed Mr Jones, I didn’t get a response.’”

Parents were also putting pressure on teachers, he said, in some cases even asking for instant help with tricky homework. Parents were getting in touch saying: “this is urgent and I expect an immediate response”, but “parental expectations need to be properly managed”, said Roach.

The general secretary used his conference speech to accuse independent schools of using “gun to the head” employment practices, threatening to fire and rehire staff in a dispute over pensions. Roach accused them of treating teachers with “contempt and intimidation”, and said if they continued, there should be a rethink of tax breaks for private schools.

Teachers at the GDST, a group of 23 private schools, went on strike earlier this year over their schools’ withdrawal from the Teachers’ Pension Scheme (TPS). In March, the trust said teachers would be able to stay in the TPS, but new teachers would not be allowed to join, and withdrew the threat of pursuing “fire and rehire” policies.