And, even though we might not have understood why it was important to say these words which we parroted out whenever we were shown a kindness when we were kids, our parents were unwittingly introducing us to a modern day psychological phenomenon; gratitude.

Practitioners promise that gratitude is the pathway to achieving a more fulfilling life through promoting a more positive mindset.

It is more complex than just vacuously exclaiming how thankful you are for everything around you: 'Thank you trees for giving me shade.' Rather it is an appreciation of what we have as opposed to what we want, a radical shift in thinking in our consumerist society.

But the concept can have wider applications than for self-obsessed millennials worrying about the avocado shortage.

Studies suggest it could do more than just reduce our desire for retail therapy but also increase our energy levels, optimism, mood and empathy, as well as improving mental health and reducing anti-social behaviour and can have positive results with students.

Anything which can possibly help pupils have a more satisfied life is worth challenging the average teacher's cynical desire to dismiss such concepts as 'new-age rubbish'.

Research carried out by California State University in 2012 is encouraging for those considering introducing gratitude into the classroom.

“Gratitude played an important role in many areas of positive mental health of the teens in our study,” according to psychology Professor Giacomo Bono.

“Increases in gratitude over a four-year period were significantly related to improvements in life satisfaction, happiness, positive attitudes and hope,” he added.

The research tracked 700 teenagers growing up in New York City and found that grateful teens are more likely than their less grateful peers to be happy, less likely to abuse drink and drugs and less likely to be in trouble at school due to their behaviour.

Within the classroom, this has caused me to alter my practice.

Previously I would  hand out the books and materials myself simply because I found it quicker to do, but now I ask individual pupils to do so and then express my gratitude to them for doing something concrete.

This models the concept to the pupils who will hopefully want to pass on their thanks to others.

Practical examples of the benefits of gratitude can easily be found around the school community; ask a pupil to buddy a new pupil for their first couple of days at school and you can visibly see the pleasure they get from being given the responsibility.

Even asking the most troubled teenager to hand out the folders to the class can elicit a positive spark.

Teaching pupils who have moved to the United Kingdom's education system from elsewhere in Europe has given me further evidence of how gratitude can have positive effects on how a group thinks.

The Eastern European teenagers I have taught generally seem genuinely grateful to experience our free education system and often seem surprised that their new classmates don't share their commitment to getting the most out of their education.

Their appreciation rubs off on the native pupils who previously had taken their education for granted. 

In previous years, in an attempt to get my pupils to value their education I have told them the monetary value of it.

My thinking was that they knew the cost of everything or if they didn't, would want to find out: 'That's a really nice phone; how much did you pay for it?'

Perhaps knowing how much was spent on them by the government each year would make them want to make the most of the state's investment.

They didn't. On the other hand, pointing out how someone has sacrificed time or pleasure just for them, such as a member of support staff fetching their lunch for them or a classmate allowing them to take first turn on the computer, does give them cause to be grateful.

Trying to make my approach to gratitude more systematic, I encouraged a class of 15-year-olds to start a gratitude journal, the classic method used by practitioners to promote gratefulness, where at the start of each lesson the class would list five things they were thankful for.

Despite their grumbles, this group of generally cynical teenagers have all taken the task seriously, which was my first surprise.

While their responses are not as effusive as the lists I have seen on the more Californian websites: 'Thank you for the nutritious lunch made by loving hands' , of the Caledonian lists I have seen, a nice genuine sense of innocent gratefulness occur, 'My mum', 'sunshine', and 'riding my bike' have all been listed in different top five lists.

"Sir, aren't going to do that thing today?" I was asked one morning which made me realise that this simple task has had some kind of immediate impact.

The class seem to settle down more quickly to work with fewer complaints and the mood in the classroom seems to be brighter.

Something else I noticed was fewer members of the class asking out to the toilet, could this be because the pupils are feeling a bit less stressed and don't feel the need to escape for a few minutes?

A next step could be for the class to write a letter to someone they feel grateful to, perhaps for helping them in the past.

Another American classroom experiment compared students who wrote these letters and then read them to the recipient with others who didn't write.

The study found that the letter-writers immediately experienced more positive emotions, which remained with them two months after the letter.

As depression amongst teenagers all over the world remains a growing problem, anything, no matter how left-field, which could have a positive impact on mood, is surely worth at least trying.