Sir Ken Gibson said he was determined to drive up standards at Harton Academy in South Shields – and insisted the dress code was fair and affordable.
Several mums and dads have taken to social media and other channels to voice concern at an initiative due to take effect in September.
All year 7, 8 and 9 youngsters will be required to wear a shirt, tie, navy blazer, smart trousers or skirt, with a jumper being optional.
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Older pupils will have the same outfit but with the option of a blazer or jumper, and all girls can wear trousers or a choice of two skirts.
Students are currently required to wear a polo top or sweatshirt and smart trousers or a skirt of their choice.
Some parents have questioned an alleged lack of consultation, possible higher costs, and the choice of a supplier based in the west of Newcastle.
But Sir Ken insisted a full consultation had taken place, including a meeting attended by around 500 parents, and that information emails and letters had been sent.
And he said surveys had shown 66.5 per cent of pupils and 91 per cent of staff at the 1,600-pupil school, in Lisle Road, supported the switch to a uniform that would cost about £50.
One parent told the Gazette: “I agree with school uniforms, but I also believe due consideration should be given to cost and local availability, and the financial implications to parents.
“Harton abolished the school tie and blazer many moons ago, saying it had become too time consuming for teachers to police. So, what has changed?”
But Sir Ken said: “Standards have fallen in recent years and some pupils wear inappropriate clothing.
“There was a wide consultation of students, teachers and parents, some who approached me to ask about the change but who were supportive when it has been explained.
“We did look at a number of suppliers and decided the company we have chosen was best. We’ve done everything as well as we possibly can.
“I do understand that costs are a concern to some parents, and we have payment scheme available and will also look at other support to some people.
“But the time is right for a higher standard of dress in line with being an outstanding school. I think the pupils are going to look fantastic.”
The Department for Education has no statutory rules around uniforms, but its guidance includes that schools try to source locally and consider costs.