Teachers are spending more time marking and planning than in the classroom, an Ofsted survey has revealed, as heavy workloads leave them cramming jobs into their free time.
Full-time staff are giving lessons to pupils for an average of 22 hours every week and spending the remaining 29 hours doing "non-teaching tasks".
This means just 43 per cent of their time is spent teaching, while the rest is used to plan lessons (13 per cent), mark work (11 per cent) and complete administrative jobs (seven per cent).
Teachers are so overworked that they left with little option but to use their evenings, weekends and holidays to catch up, the survey of more than 4,300 staff members across 290 schools and 67 further education providers revealed.
Ofsted's report on the findings, published today, also pinpointed "challenging behaviour of pupils" and "abusive and disrespectful" treatment of teachers by parents as sources of stress.
Fidgeting, humming and whispering during lessons was reported by 87 per cent of those surveyed while 32 per cent said they had experienced intimidation or verbal abuse.
Absenteeism - unjustified absences from school - was flagged as an issue by 69 per cent of respondents and "mindless vandalism" was one of the problems raised by staff.
One in 10 respondents said that alcohol or drugs were found on or used by school pupils daily, weekly or monthly. This rose to 21 per cent among students in further education colleges.
Other issues highlighted by the report include "unwanted electronic contact among pupils" and "postings of hurtful information on the internet about pupils".
Meanwhile aggressive behaviour by parents was found to be among the top causes of moderate or high undue stress at work.
The report describes them shouting at teachers, leading to a "mob mentality" as other parents witness the incident and escalate the row.
An "immediate response culture" and open access to staff email addresses also means parents expect their queries and complaints to be dealt with instantly.
It is such a significant problem that the report suggests schools might consider restricting parents' access to staff email addresses and try talking to them face-to-face or on the phone instead.
One teacher quoted in the report said they dreaded sifting through messages, adding: "My email inbox is like a pit of death. My emails are incessant. I often receive 50-80 emails per day, even when I am ill.
"Parents email at night and want an instant response that night. If you don’t respond that night, they phone the school the next day".
Pushy parents who want their children to get top results are also a challenge, with the report stating: "Expectations become a problem when they are perceived to be unrealistic or unfair – when parents expect the highest grades for their children despite their lack of effort.
"Staff are under pressure to ‘do everything under the sun for one child’ or help ‘all pupils get all A-star grades’."
In one school, it was said that 40 per cent of children had social, emotional and mental health difficulties which are often rooted in their parents' behaviour.
The report points out that it can just be an "odd few parents" who "bring a school down", and that this adds "another layer of complexity" to dealing with unruly pupils.
These findings follow the announcement of a crackdown on bad behaviour in schools by ministers earlier this year, with £10m earmarked to help advise schools how to improve issues such as pupil attendance, punctuality and detention systems.
If a pupil is persistently late without a valid reason, this may lead to the parent being issued with a penalty notice or prosecuted.