A Norwich school has become one of the first in the country to get a no-notice behavioural inspection as Ofsted aims to prevent troublesome pupils being hidden away.

Gavin Bellamy, left, headteacher at Sewell Park College in the north of the city, said inspectors saw teachers and pupils 'just as they are' when they arrived last week following a phone call just 10 minutes before – and he was delighted with the result. The report of the visit, on October 11, was today set to be published with a letter posted to parents last night.

In it, Mr Bellamy described the visit as a 'huge success for the college' with inspectors impressed by the progress being made at the school, particularly in terms of behaviour.

He told the Evening News: 'We are absolutely delighted Ofsted have validated what we already knew. We made excellent progress against all our targets.

'Ofsted found our behavioural management system to have had a very positive impact in a very short space of time.'

The trial of no-notice monitoring inspections were recently announced by the inspectorate for 'satisfactory' schools – like Sewell Park College – where there are worries about pupil behaviour.

It follows concerns raised by education secretary Michael Gove that some schools took naughty children on trips to get them out of the building when given warning of an inspection.

A spokesman for Ofsted said the unannounced visit to the Constitution Hill school was part of the first batch of trial inspections carried out over the past couple of weeks which aim to get a 'clearer picture of behaviour in schools'.

In his report, Paul Brooke, who visited for one day along with fellow inspector Michael Stanton, said he had concentrated on the key problem areas highlighted during Sewell Park's last full inspection in June 2010.

At that time, the school was told it needed to overhaul its behaviour policies within six months, ensure internally excluded students were still working during the exclusion period within 12 months, and raise attainment to at least the national level within 24 months.

Following last week's no-notice visit, Mr Brooke rated the school good in terms of its progress in making improvements, capacity for continued improvement and effectiveness in improving pupils' behaviour.

Standards, although still below the national average, are 'rising steadily and sustainably' with 'attainment on a strong trajectory of improvement for 2012 and beyond'.

The inspector praised the use of better assessment, the headteacher's impact on raising expectations among students, staff and parents, and the school's robust approach to pupil behaviour.

He added: 'Expectations about punctuality, attendance, behaviour and participation in lessons have been clarified so that students are in no doubt about what is acceptable and are aware of the consequences of transgression.'

In his letter to parents, Mr Bellamy told them Ofsted had 'found us as we would be on an ordinary day in college'.

He thanked staff, students and pupils for their support in recent months as the school sought to make speedy improvements.

The headteacher said: 'We are working together to transform expectations and opportunities for the young people of our community.'

Last night Alison Thomas, county council cabinet member for children's services, congratulated Sewell Park College.

She said: 'The school has been working really hard over the last year to ensure it has effective behaviour strategies in place, that there is consistency across the school and that students have good attitudes to learning.'

The councillor said that work had been strengthened since the arrival of Mr Bellamy in April.