Last week, Unity College sent a newsletter to parents telling them children must attend school in full uniform but despite that, a number of children fell foul of the school's policy.

Yesterday those who were not dressed according to its uniform code were either sent home or, if their parents could not be contacted, put "into isolation" to continue with their work.

Howard Parkinson, a spokesman for the college in Trinity Avenue, said: "Some children have been sent home because they weren't wearing correct uniform and those whose parents we couldn't contact were put in isolation.

"All the principal is trying to do is to enforce the raising of standards. We sent out a newsletter to parents saying children must turn up in full uniform. It specifically said trainers were not allowed unless they were completely black. We have been strict on enforcing the rules because we want to get it right from day one.

"It is only a couple of handfuls, a small number of people. Children have gone home and changed into the correct uniform and then come back into school, so they missed out on schooling for a matter of minutes.

"A couple of parents told us not to send their children home and brought in the correct uniform."

He said those students who were taken out of lessons continued with their learning in isolation and added that overall, the message had got out to both students and parents regarding the new uniform.

Mr Parkinson said: "We have been really, really pleased with the number of children with full uniform and fully prepared. We have had a good response from parents.

"The principal has taken a decision that we will enforce good uniform standards and by wearing the correct uniform, students show they are prepared to learn and raise standards, and parents have taken it on board."

Mr Parkinson said the school, which is in special measures, was keen to ensure the uniform was priced at a reasonable level.

The uniform comprises black shoes, black trousers or skirt, and college sweatshirts and shirts with the college logo.

One parent, whose 14-year-old son was sent home for wearing the wrong shoes, said: "I think they should wear a uniform, it's just the way they're being really picky about it.

"His shoes are black with a little white tick and they told him if he colours it in, that's okay. I'm really angry, it's just picky."