“Instead, they made her sit in reception until I could get away from work and come collect her. It completely undermines what the day was supposed to be about.”

Bilton School’s leadership has since apologised over the incident.

Stowe Valley Trust’s statement in full:

“At Bilton School, we are proud of the diversity of our students and the rich heritage they bring to our community. We are committed to fostering an environment where every pupil feels respected, valued, and included.

“On Friday 11th July, an incident occurred during our Culture Celebration Day that caused considerable upset to one of our pupils, her family, and members of the wider community.

“We deeply regret the distress this has caused and offer our sincere and unreserved apologies.

“We have since spoken directly with the pupil and her family to listen to their concerns and reflect on how this could have been handled better.

“We are committed to learning from this experience and ensuring that every student feels recognised and supported when expressing pride in their heritage.

“As a school, we are reviewing our policies and strengthening staff training to ensure our practices reflect our values of inclusion, respect, and understanding for all.”

The event had been billed as a celebration of cultural heritage, with a permission letter telling parents the day aimed to promote “inclusion, understanding, and appreciation of different backgrounds, traditions and heritages.”

But Mr Field claimed the school’s actions did the opposite, and that other pupils were also turned away for wearing items representing the UK.

“Courtney chose the dress herself and wrote a speech to go with it,” he added. “She was proud of what she’d put together.

“Then at 9am I get a call saying she’s been pulled out because it’s ‘unacceptable’. I couldn’t leave work until midday, so she sat there in isolation in front of the reception staff for hours.

“She’s never been in trouble. Straight A student. One of the brightest in her year. She was devastated.

“I asked the school for an explanation and couldn’t get a straight answer. Her head of year said he wasn’t the right person to speak to — which tells me he probably didn’t agree with it either.”

Mr Field claimed Courtney wasn’t the only one singled out.

“One child dressed in traditional farming clothes — flat cap and checked shirt — wasn’t allowed in. Another with a St George’s flag. One had a Welsh flag. All turned away.

“It felt like anything remotely British was deemed unacceptable. Yet pupils in burkas, niqabs, or Nigerian traditional dress were allowed through.

“They didn’t even listen to Courtney’s speech, which was actually about inclusivity and celebrating all cultures. It just felt like being British wasn’t something that could be celebrated.

“The governors eventually got involved and the school backed down and apologised. But by then the damage was done.”

The secondary school, a sponsored academy under the Stowe Valley Multi Academy Trust, features a welcome from headteacher Jayne Delves on its website, saying it is “proud to work together in nurturing and developing the potential for all young people”.

“Our student population is ethnically diverse. We have students from every corner of the globe, students from the local area plus our staff, forming the Bilton school family,” it adds.

“A family which nurtures and develops every talent and is always there to provide support and celebrate achievements. We aim to develop happy, confident and successful students for whom we are ambitious in their seven-year journey with us.”