Mount Carmel Roman Catholic High School pupils are
frequently reminded of its rules, the head teacher said
Two teenage boys have been barred from classes because they refused to shave off their beards.
The 14-year-old Muslim pupils were placed in "isolation" from the start of the new term at Mount Carmel Roman Catholic High School in Accrington, Lancashire.
Head teacher Xavier Bowers said the decision was not a religious issue.
He said it was policy to place pupils in a learning support centre when they do not comply with the school uniform.
In a statement issued by Lancashire County Council, Mr Bowers said: "I am fully aware of the sensitive nature of this issue and have done my very best to be as understanding and reasonable as possible when dealing with situations of this nature.
"When necessary, we place pupils in our learning support centre who do not comply with our school policy regarding uniform and appearance.
"Here at Mount Carmel RC High School, we believe that it's important to maintain high standards in every aspect of school life, including appearance and uniform."
He added pupils and parents were frequently reminded of the rules on appearance.