When we were young teachers a wise woman told us that we should never ask the children to tell the class what they did for Easter or Christmas or Confirmation or St Patrick's Day.
Don't ask, she said, because it will turn out that some of them did nothing at all or - worse still - had a really awful time. Nothing points up the inequality of people's lives more starkly than asking innocent children to tell you how they spent what was meant to be a festival.
But once I forgot this and asked them what they did for the National Day.
There was the usual chorus of visiting granny and going to watch the parade and having lunch in a hotel from the lucky ones. And then there was a child who said they spent the whole day looking for a vet's that might be open because their dog had got hurted.
And I asked what had happened to hurt the dog.
Later you get a sense of what not to ask, but you don't have it when you're 22 and eager to be nice to the children and encourage them to tell stories.
It was a tale of a brother who had been away at sea coming home unexpectedly and his not liking the fact that Mammy's friend was living in the house and breaking a chair, and the dog got frightened and ran under the table whining.
And there had been a fight between the girl's brother and her Mammy's friend, and the dog hadn't understood so he jumped at the brother not realising who he was and to save himself her brother had picked up a bread knife and the dog was badly hurted.
And we all sat in that classroom as the horror of someone else's St Patrick's Day came through to us.
And I remember her voice going on about it not being too bad in the end because eventually she and her sister brought the dog to a hospital - a hospital for people - and someone there knew a vet nearby, so they carried the dog to his house and he stitched the cut in the shoulder and the dog would limp always on his front left paw and he had a bit of a cough but he was not going to die which they thought he might when they saw all the blood. I wonder do any of the other pupils remember her telling that story? She is dead now, so I can tell it without hurting her.
She left school without any real education or exams, nothing much at home to encourage her, and she married when she was 19 - to a very nice fellow apparently, and they had a grand marriage until she died at the age of 38, some complications after a routine operation.
I'm sure that during the years of her happy marriage she didn't keep thinking back to that terrible St Patrick's Day in l962 when she and her little sister carried a big dog covered in blood all around Dublin and eventually going to a hospital for people.
Maybe even the sadness and fright of the Domestic Incident had long died down in her mind.
Not in mine.
I think of it every St Patrick's Day when I see the Special Menus advertised in hotels, when I hear the oompah-oompah of a band. Not because I want to superimpose on everyone else's happiness the image of those two frightened little girls whose dog always coughed and walked with a limp as a result of the day's events.
I suppose it's just to remind us not to assume.
It certainly cemented the lesson that the wise old teacher had taught us, and now that I'm not in the classroom any more it hasn't lost its relevance. I strongly believe that you don't do thoughtless, cheerful vox pops to people about feast days.
In spite of the greeting cards, the streamers, the cheerleaders and the festivities, a startling number of people may have remarkably little to celebrate.
And all this came to mind because I met a glowing young girl with a tape recorder who was doing a series of ad-lib recordings in a shopping mall for a radio programme.
She thrust her microphone at passers-by and with a huge infectious grin she asked every one of them "What will YOU be doing on St Patrick's Day?" Her tone expected a reaction of riotous excitement, fun, happy families and carnival time.
In my earshot she met a man who would be going to see his wife up in the hospital as usual.
She met a woman who said she was going to stay in bed all day with the sheet up to her chin because she was demented with all the demands her children were making.
She met an elderly woman who said she wouldn't be doing much because she had been broken into and robbed.
In one way I wished the gorgeous girl with the microphone might realise that not everybody on this windy day was gearing up to a party-party spirit. That she was unearthing more despair than hope.
But then as a co-worker I was sort of sorry for her. I know what it's like when people won't say what you want them to, when they refuse to behave like a crowd sent down by Central Casting who are mouthing exactly what you want to hear.
But finally she met another gorgeous young girl like herself.
"I'm a SINBAD, I'll be cruising Temple Bar," said the interviewee, which seemed to satisfy the girl with the microphone perfectly.
But not me.
"Excuse me," I said coming out of hiding from my lurking position. "What's a SINBAD?"
Apparently it's a Single Income No Boyfriend, Absolutely Desperate. But then everyone knew that, didn't they?