Every morning and afternoon it's the same: instead of just dropping their kids off, or scooping them up from the classroom door, they always find some reason to engage the teacher in conversation.
What can they possibly have to say that can be so important?
Cristina, mum to grown-up Lara, agrees it's irritating. "It's a symptom of a selfish society," she says. "People forget there are 30 children in the class and the teacher needs to attend to all of them, not just the precious off-spring of one mum."
My point exactly: it's simply not fair on the rest of us.
At my school there is a parents' evening once a term, but that's clearly not enough for some mums, who race across the playground each morning, desperately trying to grab Miss Jones before anyone else does.
Poor Miss Jones is trying to drink a cup of tea, supervise playground antics and, no doubt, plan the day's activities in her head, so surely the last thing she wants is to be accosted by an over-anxious parent?
Moreover, with so much going on, and so many pairs of interested ears hovering around, the playground simply isn't the place for important discussions.
If what you have to say is crucial to your child's development, then book an appointment. If it isn't, leave it, or ask another parent – they'll almost certainly have the answer.
Teacher Kate says it's quite simple. "If there's a problem with little Johnny, I'll tell you. Otherwise, just drop your kids and go."
I'm happy with that: I trust the teachers to tell me if there's a problem, and I rely on my own parenting instincts to judge whether my children are settled. If you can't wait till parents' evening, send a note in, but don't hog the school gate for your own private conversations.
What exactly do these mums find to talk about each morning?
Well, mum-of-one Sophie says a lot of it is down to learning the ropes. "My daughter Sarah started school this September and I'm still getting the hang of the rules, so I've got a lot of questions," she says.
"I'm trying to limit my approaches to the teachers, but it puts my mind at rest if I just have a quick chat."
This term she's collared the teacher to ask about lost property, school books and packed lunches, among other things. I can understand why the first year at school can be unsettling for mums – as well as their children – and maybe teachers need to make sure they're giving parents enough information.
At my school the children carry 'link books' to and from home so that parents and teachers can communicate on a daily basis, without the need to take over the school gate.
Laura, mum to twins Harry and George, points out that not all the school gate monopolisers are over-protective mums.
"I spend a lot of time talking to the teachers," she admits. "But that's because one of my children has special needs. It might look to others as if I'm taking up their time, but with lots of professionals involved, there's often a lot to say on both sides."
So should we assume that these school-gate hoggers aren't just helicopter parents, wasting the teachers' time with pointless questions about Olivia's special hair clips, and Max's lost jumper?
My friend Beth, mum to three children under six, is adamant I should cut them some slack. A teacher for 10 years, Beth says it is important parents aren't too harsh on their peers.
"I definitely talk to some parents more than others," she says. "But that's because of particular needs or circumstances of the child at that time. I would say to parents: don't be too quick to judge. You never know when your own child might need some extra attention and you may be the one needing to talk every day."
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