One by one, I deposited my 11, eight and five-year-olds at their various classrooms, and then turned to leave, looking forward to finally being able to work (in my bedroom) without the constant background bickering and endless requests for snacks and new batteries for festive toys.
But as I hugged my youngest son, my smile was wiped from my face by a wave of guilt – because the poor lad couldn't stop yawning. And I knew that my weak parenting was to blame.
You see, for the past couple of weeks, I've let my children's bedtimes get later and later based mainly on the mistaken logic that the later they went to bed, the longer they'd lie in the next morning which, of course, would mean that I'd get a lie-in too.
Unfortunately, children's body clocks don't work like that: when it's light, they want to play; and increasingly, when it's dark, they STILL want to play.
This seems to have had no adverse affects on the older two. The middle child, especially, bounds out of bed like Tigger on speed every morning, no matter how late he hit the sack the night before.
The trouble is, eight-year-old Tigger shares a bedroom with his five-year-old brother, who in the mornings is like Eeyore on tranquilisers.
Hence the yawning at the school gates. This has been a problem for a while. In fact, ever since my sons started sharing a room. We live in a three-bedroom flat and therefore the boys have always shared. But despite their three-year age difference, the youngest sees himself as equal on every level. And that means equal bedtimes, too.
When he was three years old, I could hoodwink him into going to bed sooner than his older sibling. But about a year ago, he wised up and so even if I put him down earlier, he'd lie awake waiting for his big brother to get into bed so he could have a good old natter.
It has now reached the point where the older boy will often call out in the night: "Da-ad, Sam won't stop talking and I'm trying to get to sleep."
The problem of tiredness at school is a common one. In fact, it's so serious that over a quarter of youngsters claim they cannot concentrate in school and even fall asleep in class at least once a week.
The study, for Travelodge, based on the sleep patterns of 2,000 children, suggested that only a third of youngsters are getting a good night's sleep. The average six-year-old goes to sleep at 9.33pm, while at eight it is 9.49pm. By the time children reach 15 the average bed time is apparently 11.52pm.
In another study, the Sleep Council surveyed 250 primary school teachers.
"We found that lack of sleep is having a devastating effect in schools with nine out of 10 teachers complaining that pupils are so tired they are unable to pay attention in class," said Jan Turner, from the Sleep Council.
"More than a third said this is a daily problem for them.
"A good night's sleep is critical for the development and well-being of young children and we believe that regular bedtimes, along with the right sort of sleeping environment - a good bed, well-ventilated room and one that is free from the distractions of TVs and electronic gadgets - is vital to achieving this."
She added that many parents are simply not strict enough about enforcing bedtimes.
That's me, guilty on all counts.
And the issue could have longer term, more serious, consequences. Writing a few years ago, Dr Luci Wiggs, a research fellow at Oxford University's Section Of Child And Adolescent Psychiatry said 10-year-olds need 8-10 hours sleep a night while four-year-olds need 12 hours.
"One of the problems with the pre-sleep activities of modern children is that they are unstructured activities, i.e. they do not have clearly defined start and end times," she said.
"This is the first generation of children to face such a plethora of alternatives to going to sleep and the long term consequences in terms of physical and mental health for both the child and their family can only be guessed at.
"What we do know is that impaired sleep quality or quantity may compromise children's physical health, academic achievements and mental health."
Lack of sleep could affect children's immune functions and growth, she said. There was also a well-established effect on memory, reaction time and concentration.
It's clearly a problem I – and many other parents – need to address. But what's the solution?
Dr Wiggs advised: "A bedtime routine should include at least 15-30 minutes of calm, soothing activities - such as reading, having a hot milky drink or a warm bath - with a definite endpoint."
Which is easier said than done when you're suffering from a case of Shared Bedroom Syndrome. Child psychologist Kenneth Condrell suggested one parent stays in the room until both children are asleep.
I suggested this to my wife when she got home from work.
"I could go to the pub while you sit up with the boys," I suggested.
For some strange reason she didn't agree.
So I tried a strategy of my own. I called a family conference (which involves me standing in the living room while the kids stare at me, blankly) and told all three that from now on after school, there would be one hour of homework and dinner, one hour of 'screen' time and one hour of bath plus calm down and chill-the heck-down time, after which, Big Sister and Big Brother would take it turns to read Little Brother a bedtime story.
Then we drew up a contract which all three unwittingly signed up for.
Three days in, it seems to be working. The youngest goes down without fuss - the power of routines and boundaries – though the older two are less enamoured.
"All this reading is so boooooooooring," said the 11-year-old.
"Why can't I play on the computer after Sam's gone to sleep?" asked the eight-year-old.
"Because I said so," I replied.
And that, for now, is that. I'm going for a lie down.
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