Denbigh High School is investigating after a video appeared online allegedly showing an exchange of text messages between two teachers swearing about pupils.
The video shows someone holding a teacher's phone, scrolling through her text messages with another teacher, in which two pupils are described as "c***s".
One of the pupils is described as a "f****** c***" while another is called a "CHIEF C***"
It is understood that on Monday, February 25, the teacher had briefly lent her phone to one of the pupils to call home, during which time he found the text messages and recorded a short video.
It is unclear what device was used to record the video. The footage has since been shared multiple times on social media.
In an angry statement posted online, one parent said: "A teacher shared her phone with a student to use and call home. The student happened to see messages pop on notifications with his name, and when he clicked, he saw the chat and recorded it.
"He's extremely hurt and upset. The teachers were referring to the 14-year-old students as 'c***s' in the messages.
"This is senior members of staff using the most disgusting terms to describe our children. The school has failed to act and has covered this up.
"So it is time we took action and remind them that we love our children irrespective of how they are and that this is not what we expect when we send them to school for them to be abused like this."
Responses on social media have been mixed, with some people taking the side of the pupils while others have defended the teachers.
One person wrote: "To talk like that about a child as a teacher to another teacher shows that she has no respect for them or the profession."
But another person commented: "It's a private conversation and it should stay private. Stressful jobs produce this kind of black humour."
Denbigh High School is part of the Chiltern Learning Trust of academies along with several other Luton schools.
Its CEO, Adrian Rogers, said: "We are aware of the incident and subsequent video that has appeared online, and a full investigation is ongoing.
"No matter how rare these incidents might be, we always fully investigate any allegation in line with our disciplinary procedures.
Denbigh High School is an outstanding school with an excellent track record and is unashamedly proud of the high standards it expects from everyone at the school."
The school currently has an 'Outstanding' rating with Ofsted and placed top of the Luton and Bedfordshire progress 8 league tables. It has been placed in the top 1% of schools in the country.