Like tie-length and top buttons, the application of make-up is a school rule students have historically ignored.
But the days of waterproof mascara, raspberry lip-balm and chipped glittery nail varnish are long gone. Students now watch make-up tutorials from beauty bloggers and celebrities from the comfort of their own bedrooms and it means they can be a little more ambitious than they would have been able to be previously.
Today's top trends? Dark defined eyebrows and contouring.
The latest make-up buzz-phrase? "On fleek."
If you're struggling to comprehend where these trends have come from and what, exactly, "fleek" means, here's a guide we put together with the assistance of our two undercover teacher reporters, Miss C and Miss K.
What makes an ‘on fleek’ eyebrow?
Back in the 1990s, thin was in. But when Cara Delevingne strutted down the catwalk a decade later, debuting thicker, fuller brows, the "power eyebrow" was born.
Gels, pencils and powder help students to achieve this look and the brow must be perfectly groomed, filled and shaped to be deemed "on fleek".
Obviously, not everyone begins as an expert. As all teachers know, practice makes perfect.
“One of the students reliably informed me that her sister's eyebrows 'fell off'," says Miss C. "She put on eyebrow gel, didn't wait for it to set then wiped it... and half her eyebrow came off."
What does ‘on fleek’ actually mean?
As for the word "fleek", it apparently originates from a 2014 Vine video and was in the running for the Oxford Dictionary’s word of 2015, losing out narrowly to "laughing emoji".
It’s most commonly applied to perfectly groomed eyebrows, but is now also being used to describe anything that’s looking particularly on point.
For example – "Sir, your hair is looking on fleek today."
And what’s 'contouring'?
"Contouring" is traditionally a technique used by drag queens, but we can thank Kim K, queen of reality television, for taking this technique global.
To contour involves using different shades of foundation on different parts of the face and then blending these shades together to enhance facial structure.
“It's all about contouring – which looks chiselled on the more skilled, and 'cakey' and odd on those who are less so,” says Miss K.
To turn up to school on a rainy Monday morning with a full face of flawless make-up is undeniably impressive, but why do students go to so much effort?
Research has revealed that almost a quarter of girls aged 7 to 10 feel the need to be perfect, and 38 per cent think that they aren’t pretty enough.
And if you think that’s a scary statistic, it’s also been reported that children as young as 3 are showing signs of being unhappy with their appearance and bodies.
Is it any wonder, then, that once they reach secondary school, where they’re judged by their peers and feel pressure to "fit in", they attempt to replicate the "in" beauty trends of the moment?
"If it helps them feel good about themselves and aids wellbeing, it's a battle I'd rather not have," says Miss K.
Miss C agrees: “The girls say that they think some students are insecure – eg, due to spots, acne, freckles they want to cover – but they also enjoy it. I think we underestimate the desire for young people to express themselves and their burgeoning identity.”
What should teachers do?
It’s not unknown for teachers to keep a pack of make-up wipes in their draw, and some schools do operate a strict no make-up policy.
But, if it helps to battle confidence issues, and doesn’t have a negative impact on learning, should teachers instead embrace the fleek?
“I think as teachers we need to be tolerant of letting them get it wrong and support them as they work out who they are," says Miss C.
Miss K says she has bigger issues to tackle, and that actually it can help to build relationships with both the students and the parents.
"I chat to the girls and their mums about nail art and make-up," she says. "My approach has been, would this be OK on a teacher? If so, yes, why not?’
In light of this, just one question needs to be asked – is your make-up on fleek?