Fancy-dress clad GCSE pupils and teachers were involved in a stand-off after reports of planned disruption forced a top comprehensive school to shut its gates.

A group of 100 Year 11 pupils from Fortismere School, dressed in colourful fancy dress costumes including Darth Vader and Big Bird, were stopped from entering the building on their last day of school before exam leave on Friday, May 18.

The school, in Tetherdown, Muswell Hill, said it had received information that “disruption” had been planned by a minority of students but refused to elaborate on details.

Teachers at the school met students head on at the school gates and asked them to go home after they marched up Muswell Hill Broadway in their costumes.

Bria Boyce, 16, said: “It is our last day in school and we want to have fun and go and say goodbye to friends and teachers.

“It’s really upsetting as we have worked hard for five years to have this one day of fun and it has been taken away from us.”

A school tradition allows Year 11 pupils to come to school in fancy dress for their final day before breaking up for exam leave in the run up to GCSEs.

But an email was reportedly sent to pupils earlier in the week saying the school would prefer if they did not dress up this year and pupils were then told on their penultimate day they would not be welcome back at school.

This provoked a rowdy reaction from the disgruntled Year 11 students whose reaction to the announcement was filmed, apparently secretly, and the clip posted on YouTube.

Despite the ban, pupils gathered on the road outside the school just after 10am on Friday and pleaded with teachers to let them in to celebrate their final day.

Ayesha Simmonds, 16, said: “We have already bought the costumes. Other years have had their day and we want ours.”

No pupils were allowed in, but the school said it would speak with parents to organise another day for pupils to say goodbye.

Headteacher Helen Anthony said: “We will have an event for those who wish to have fun and go and say goodbye to friends and teachers.

“What we will not support is disruption to the whole school. It is very sad that this is necessary.

“I felt very, very sorry for the majority of students but the bottom line is that health and safety and the smooth running of the school are of paramount concern.”

Ms Anthony also warned that the tradition of fancy dress final day was now likely to scrapped altogether as it had grown too big over the years.

She said: “I think it’s a tradition that has grown and evolved over a number of years. We have taken a good look at this and we will have a different set of arrangements over the next years.”