The guideline was drawn up by the PPTA's Rainbow Taskforce whose leader, Shawn Cooper, explained that wearing skirts often put girls off physical activities. No doubt, but that is a problem easily addressed, if it is not already, by providing a change of clothes for sports.
Women wear trousers as often as skirts these days and it is hard to believe secondary schools today would not already give girls that uniform option, if there is a demand for it. If schools don't do so, then they should.
Interestingly, when it comes to their school uniform, some girls' preferences appear to be the skirt - the longer the better for many. A Dunedin school that has already been offering boys and girls uniform options that include long or short pants, culottes or a kilt reports that only two girls choose shorts and no boys wore the kilt.
It seems something of a shame that in 2017 this matter is an issue at all.
Of course we should make generous allowance for people born with the anatomy which is not that of the gender they know themselves to be. If they are young and confused about their identity or struggling with it, schools need to be sensitive to their needs.
But equally that does not mean erasing gender distinctions in the uniforms and cultures of the school.
Whether we are male, female or transgender, no distinction is well served by denying the value of any other. The vast majority of people are unequivocally male or female and their identities are important too.