Ofsted has criticised an Islamic independent school, after inspectors found leaflets which claimed music and dancing were "acts of the devil".
Inspectors made an unannounced visit to the Darul Uloom Islamic High School in Birmingham after having previously rated the school as "inadequate".
Inspectors said pupils were not being protected from "extreme views".
But the school rejected this saying the leaflets were not in the school, but in a "mosque adjacent to the school".
A spokeswoman for the Department for Education said the allegations would be urgently investigated and that action would be taken against schools "promoting twisted ideologies".
"These leaflets should have no place in any school - and we will not hesitate to take strong action when schools focus on ideological indoctrination rather than a high-quality education," said the DFE spokeswoman.
An Ofsted inspection last year had found weaknesses with the school and inspectors returned without warning to monitor how an improvement plan was being implemented.
But a report from inspectors says that they found printed material with "extremist views".
"A large number of copies of a leaflet containing highly concerning and extremist views, such as "Music, dancing and singing are acts of devil and prohibited" were discovered during the inspection.
"The leaflets were found in areas shared by the school and adjoining mosque which are used by leaders and in areas used by the pupils from the school," said the inspectors.
But a statement from the school disputed Ofsted's claims, saying that it was incorrect to say that the leaflets had been in the school or to suggest that the school in any way endorsed these views.
The school says that the leaflets had been "clearly dumped by a member of the public" and these leaflets had no association with either the school or the mosque.
"We have a music curriculum in the school. Why would we then say that music are 'acts of the devil'? It does not make sense," said a response from the school.
"We did not or would not produce or allow any such leaflets in our school," said the school, which accused Ofsted inspectors of being "racist".
Ofsted had said that it was not clear who had produced the leaflets, which inspectors thought were calling for a boycott of a local music festival.
The leaflet is understood to have made reference to music in terms of "public indecency" and the "proliferation of sinful activities".
The inspection report of the school, which teaches boys from the ages of 11 to 16, says the school needs to put in practice its commitment to safeguarding pupils.
It also warns that there is a lack of evidence that the lessons match the published curriculum.
"For example, the policy states that the biggest timetable weighting has been given to English and mathematics, but inspection evidence and school timetables show that pupils study Arabic for approximately half of the school day."
The report says the school must take action to meet the requirements of independent school regulations.
The school was previously criticised by Ofsted for what appeared to the segregation of male and female governors.
Ofsted had reported that the school's only female governor sat in an adjacent room during meetings.
But the school challenged this, saying that the female governor was making a choice to sit separately and that this arrangement was respecting her rights.
"The right for a person to choose is a universal value," said the statement from the school.
A Department for Education spokeswoman said: "Extremism has no place in our society and when we find schools promoting twisted ideologies we will not hesitate to take action, including closing the school or working with the police if necessary."