Jim Collins, who has just taken over as principal of New College, Leicester, said he had adopted the tough stance as part of his drive to improve the school's disciplinary record and academic results.
Pupils arriving for the start of term at the 1,700-student school were greeted with posters spelling out the dress code: white shirts, school sweatshirts, black trousers and footwear without logos.
Teachers policed every entrance barring any pupil incorrectly dressed. A fleet of mini-coaches was waiting to return them home.
Jon Dickens, whose 12-year-old son Nathan failed to make it in because he had white Umbro logos on his black trainers, said: "Nobody told us that they had sent him home, so he could have been left walking the streets."
However, Mr Collins, formerly Birmingham's assistant director of education, said pupils and parents had been given advance warning about the policy, which he intended to continue to enforce. The message had been driven home at several assemblies last term, and he had also written to every parent over the holidays.
He said: "The correct uniform is an indicator of good discipline, and gives pupils a sense of identification. A number of parents, including 300 at a parents' evening who burst into applause when I announced it, are very pleased that the policy is to be enforced."
Mr Collins, who has succeeded former Secondary Heads Association president Judith Mullen as principal, said that the uniform policy was one of a number of measures planned to raise standards, including changes to help teachers monitor pupil behaviour.
Although the school was taken out of special measures last term, this year it has the worst GCSE results in Leicester, with only 14 per cent of pupils getting five Cs or better.
New College was founded in 1998 by merging three schools under the Government's controversial Fresh Start policy. It is now the largest Fresh Start school in the country.