A substantial number say they are intimidated by the "big brother" approach of over-zealous management and nearly 10 per cent complained it amounted to harassment and bullying.
The findings are based on a questionnaire returned by members of the National Association of Schoolmasters Union of Women Teachers in 400 schools.
Just under half of the secondary and primary teachers who responded said they were observed once a year. Around 30 per cent were monitored once a term. But in primaries the proportion of teachers observed in class more than once a term was 30 per cent, compared with 23 per cent in secondary schools.
While most teachers thought the amount of observation was reasonable, 39 per cent of primary respondents and 22 per cent of secondary respondents considered it excessive.
Teachers generally accepted observation by heads or deputies, curriculum coordinators and education authority advisers as part of school improvement programmes, professional development and appraisals.
But the 25 per cent of teachers - mostly in primary schools - observed by shool governors felt that it was unacceptable that governors should usurp the management role of the headteacher.
Nigel de Gruchy, NASUWT general secretary, said: "Teachers do not object to their work being observed and monitored if it is done by other professionals for sound reasons.
"Too frequent observations can appear as bullying, and the fact that 9 per cent of teachers feel harassed by their schools' practices is a serious problem that must be addressed.
"Snapshot observations once each term or more extensive observations annually would be regarded by most teachers as reasonable."
Inspections of teachers' lesson plans and pupils' work by heads and senior staff was also felt to be over the top in primary schools.
Half of the respondents had to submit work for weekly checks, compared to 10 per cent in secondary schools.
The association has called for an immediate halt to the practice.
Mr de Gruchy said: "Subjecting nearly half of all primary teachers to weekly monitoring of lesson plans is way over the top. It flies in the face of anti-bureaucracy Government circulars and should cease."
The questionnaire was sent to about 1,600 association representatives in schools.