Ms Hayward said the initiative came from the pupils.
Since arriving at the school 18 months ago, she had received requests from girls to wear something other than the school kilt.
"Last year I had a couple of kids who challenged me. They said: `Why do we have to wear kilts? You can wear pants. Why can't we'?
"That seemed pretty logical to me. It was 2016 and I thought it was odd that we still have these stereotypes. What we were hoping to avoid is making it hard.
"If you're a girl who doesn't want to wear a skirt, you should have an option that works for you. That's where the culottes come in,'' she said.
Girls could also wear long pants in the winter if they wanted to, and boys could wear kilts, like their Scottish ancestors.
Pupil Ella Clarke said she was looking forward to wearing long pants in the winter.
"That will be good when it gets really cold.''
In a bid to make the uniform more cost-efficient and recyclable, the school jersey was the same as the Logan Park High School jersey, Ms Hayward said.
"A large number of the DNI kids go on to Logan Park, and the DNI monogram can easily be replaced with a Logan Park monogram.''
She said the pupils had been accepting of the options, but parents had taken longer to warm to the initiative.
"The kids weren't really fussed about it. It's adults that have taken a while to get their heads around it - they've asked lots of questions.''