It’s parents’ evening and I’m sitting across the table from Laura and her dad. They are the spitting image of each other: slight, dark-haired, and scowling. I’m smiling encouragingly as Laura’s dad rants at me. Inside, I’m white-hot with rage. I’ve been royally stitched up.

“Laura tells me you’ve been ignoring her pleas for help in lessons, and that some days you won’t even speak to her. I’m not surprised she’s not making progress. You clearly just can’t be bothered any more. Call yourself a head of maths? She says she’s learned more from the TA from you.”

Laura can’t hide a little smirk beneath the fringe. I think back to yesterday’s lesson, where she wrote “Miss is a bitch” painstakingly all over her GCSE paper, for an hour, instead of answering the questions. The lesson before, where I sat with her patiently trying to explain prime numbers while she stared at the wall and suggested I shut up. I interrupt Laura’s dad and explain that Laura is quietly disruptive in lessons, that her stories of me ignoring her are outright lies. His face darkens and the conversation turns ugly. The deputy head arrives to deal with his concerns, but now the battle lines have been drawn. He sees me as the enemy, and believes that his daughter would never tell an untruth. The rest of the term will be spent with me trying to placate him, while helping his daughter get her predicted C-grade.

As teachers, we expect pupils to lie from time to time and we deal with them accordingly, teaching explicitly through PSHE or indirectly modelling the behaviour we expect. We show them how to face up to mistakes and admit errors; we resolve disputes and guide them towards honest relationships. But everything gets much more complicated when a child like Laura’s lies are accepted by a parent as truth.

This is particularly topical: a scientific study has confirmed this week that parents are terrible at spotting when their own offspring are lying. Parents were asked to look at videos of their own children and state whether they were telling the truth or not. Students and other parents were asked the same questions about the same videos, and the answers were compared. Parents correctly assessed that their own child was lying just 8% of the time – compared with the other groups, whose accuracy was 43% and 44%. “These findings … suggest that the close relationship that parents share with their own children may be related to a bias toward believing their children’s statements and, hence, a failure to detect their lies,” said lead author Angela Evans.

I’ve had children say I wouldn’t let them go to the toilet, or that they definitely didn’t steal my pen

I’ve had children say I wouldn’t let them go to the toilet, or that they definitely didn’t steal my pen (then later look shocked when it turned up in their pencil case). Similarly, the line can be blurred. We can all relate to the sinking feeling you get when a child in a lesson being observed by a senior staff member is asked “and what are you supposed to be doing?” and they reply: “No idea.” Is this the truth, a careless lie, or – much worse – a knowing one?

The implications could be career-shattering. Figures from 2011 suggest at least 2,827 allegations were made against teachers in that year, along with 1,709 against non-teaching staff. Around a third of these were found to be substantiated, leaving two-thirds that were unfounded, malicious or simply inconclusive. Of course, by the time such allegations reach investigation, it is not just the parents who are assessing the child’s story; however, they are usually the first person the child tells and as such it is crucial for teachers that parents are able to accurately evaluate their child’s story.

As a parent as well as a teacher, however, I’m struggling. I know that not believing a child when they are telling the truth can be extraordinarily damaging. Like many parents, one of my priorities is making sure my children can talk to me about anything. I have no doubt that the “truth bias” from the study exists – it took finding a heap of sweet wrappers under my daughter’s bed for me to realise she had been stringing me along for several months – but that doesn’t help me when faced with a persuasive little face and a quick decision. It should be about balancing the knowledge that we aren’t good at detecting our children’s lies, with the need to be open to them when they confide in us.

The key has to be in creating a climate – both at home and in the classroom – where we actively discuss why we lie and when it is and isn’t OK. From a young age, parents and teachers must share some of the responsibility for schooling children to believe that deception is wrong and honesty is right. This is when the children see us, their adult role models, tell white and not-so-white lies. We tell Uncle Henry his haircut looks great; we tell our friend Helen we can’t make it out today because our child is sick; we tell another teacher that we can’t do their break-time duty because we have a bad back. We do our children a great disservice by failing to talk to them about this inconsistency and thinking they won’t notice.

After all, as we all know, children lie to save face, to get out of trouble, and sometimes because they have started a habit they can’t stop. A good way to prevent the first two turning into the second might be by changing the way we speak to children: instead of “Are you telling the truth?” (forcing them into a defensive position), say that you understand it’s difficult to be honest but it’s better to be open. Parents and teachers shouldn’t be afraid to tell children about the times they have experienced the same thing, and above all praise honesty rather than react snappily to bad behaviour.

But most of all, parents please remember that teachers are on the same side as you: we too want to help children develop in the right way, so trust us when we tell you your beloved is fibbing. And if you’re wondering, Laura eventually cracked after I sat her down and told her the implications of her actions. In fact, we’re still in touch – her lie was a symptom of her own personal issues, as such things often are. She’s now a waitress at my local cafe. Sometimes the service isn’t great, but I haven’t ratted on her – yet.