After more than two months of leaks and allegations, the first results of the multiple investigations into the Trojan horse allegations arrived on Monday via Ofsted's inspectors – revealing some startling evidence, amid a wide net of concern about exposure to extremism and cultural isolation.

Of the 21 schools in Birmingham inspected over concerns of a citywide plot, five were punished with special measures by Ofsted inspectors, swiftly followed by the Department for Education (DfE) issuing formal letters of intent to terminate the funding agreements of the four academies involved – a prelude to a change of control. A total of 11 other schools were said to require improvement.

Apart from one school – Oldknow primary – the criticism was not so much about the schools' activities but what they did not teach. In most cases, inspectors found that pupils were not taught about the risks of exposure to extremism. In several others the concern was compounded by a fear the pupils were culturally isolated – divorced from what was described as life in modern, multicultural Britain.

Several of the schools rejected the allegations, with Park View academy, in particular, producing a long list of the social and cultural interactions that pupils enjoyed, including the Scouts and boating trips to Norfolk. But in other cases the inspectors saw a trend summarised by Sir Michael Wilshaw as "emotional dislocation from wider society".

Arguably the most striking evidence of danger comes from the inspection of Oldknow primary, a large school with mainly Muslim pupils, rated as outstanding by Ofsted as recently as last year and praised even now for high-quality teaching and achievement.

At Oldknow the Ofsted inspectors agreed with the more detailed findings of the DfE's own inspectors, whose report was also published on Monday for the first time.

Inspectors highlighted £50,000 the school spent on a trip to Saudi Arabia, which took in the Umrah pilgrimage as the pupils visited the holy cities of Mecca and Medina. Non-Muslim pupils were excluded from participation. In the DfE report, the Education Funding Agency inspectors concluded: "This does not accord with providing the best education and wider societal outcomes and we consider that [Oldknow's] trust did not demonstrate value for money in arranging the trip."

To Ofsted, the trip to Saudi Arabia – one of three the school has organised – was significant in that pupils from other faiths were not able to take part. It concluded: "A small group of governors is making significant changes to the ethos and culture of the academy without full consultation. They are endeavouring to promote a particular and narrow faith-based ideology in what is a maintained and non-faith academy."

Combined, the Ofsted and EFA reports chart a school that has changed rapidly in the course of a year, after a change of staff and the resignation of a previous head teacher and senior staff.

The EFA reported that one teacher would not shake hands with a female member of the inspection team – a sign of religious observance among Salafist Muslims rather than extremism, but the EFA noted: "Based on the views that he expressed to us, we concluded it would be difficult for this individual to keep those views separate from his teaching."

Cancellation of Christmas events, the curtailing of exchange visits with nearby churches, the decision not to have a tombola or raffles at the school fete, all within the previous year, led the EFA team to conclude: "We saw evidence that Oldknow academy is acting as a faith school and is not making active efforts to make the academy attractive to all faith denominations including pupils of no faith." Oldknow's acting principal, Jahangir Akbar, said the allegations against the school were false or exaggerated.

The evidence at other schools was less graphic. Typical was the Ofsted report on Nansen primary – part of the Park View Educational Trust. At Nansen, inspectors complained the school was failing to "develop pupils' awareness of the risks of extremism or radicalisation" – a common theme among the remaining schools.

At Nansen pupils were "at risk of cultural isolation" and the school's leaders did not "sufficiently develop pupils' understanding of the different customs, traditions or religions" of the UK. "This does not prepare pupils adequately for life in modern Britain," the inspectors said.

Similarly, at Park View academy – Nansen's sister school – the school failed to "raise students' awareness of the risks of extremism". The theme of social and cultural isolation also reappeared: "There are few opportunities for students to learn about different types of beliefs and cultures in the older year groups.

"Students are not taught citizenship well enough or prepared properly for life in a diverse and multicultural society."

At Golden Hillock, another school governed by the Park View trust, the inspectors concluded: "Too little is done to keep students safe from the risks associated with extremist views."

It said staff had only recently been trained in recognising signs of radicalisation and extremism.

Alone of the five schools placed in special measures, Saltley secondary's weaknesses had already been identified by Ofsted, which outlined a disastrous breakdown in relations between staff and governors in November last year.