But somehow we do - oh boy, do we! We parents seem increasingly anxious to shoulder the whole burden of our children's education - with anxious being the operative word.
Take my tennis group. Two were off recently with nervous stomachs because their daughters were taking GCSE. "History wasn't too bad," confided one mother, anxiously, "but we found music just awful."
Then there was the mother in the school car-park, who suddenly clapped her hand to her forehead and cried, "Oh heavens, it's their big physics test tomorrow, isn't it? And Glyn's lost his book. I'm going to find Mr Sandwell. There's no way I'm having him take that test without him having done the right revision." And off she sped to do battle in the physics lab.
"Do you have a physics test tomorrow?" I demanded of my son (anxiously) when he came slopping out of the door.
He searched the windy spaces of his brain. "Oh - yeah. Think so."
"Have you done your revision?" "Yeah. Well - no. I'll do it tonight."
"The Crystal Maze is on tonight," piped his sister, unhelpfully.
"Yeah, well. I'll do it after," he drawled, sprawling into the car.
Did he? I'm ashamed to say I have no idea. I meant to ask him, I really did, but then what with one thing and another - adult things - it quite slipped my mind until about three weeks later when it somehow seemed too late to ask.
Part of me says this is exactly as it should be. I don't remember my parents ever showing the slightest interest in my homework, and it didn't do me any harm. And how's a child to learn independence and self-reliance if his mother is at his elbow every minute, guiding his pen along the lines?
But another part says that's just laziness because every parent I ever meet seems to know more about their children's reading schemes, history curriculum, and how next year's maths classes are to be divided up, than I do. And that's probably because they've understood far better than I how times have changed, and how yesterday's heedless ways simply won't do in the light of today's harsh new realities.
Because in these days of league tables and expanded higher education, children need all the help they can get.
If they don't start off well at primary school, they miss out on the enrichment programmes later. If they perform poorly at secondary level, they don't get into the fast track for maths and English. GCSE course work makes greater demands on their out-of-school resources than any amount of rote exam learning ever did, and everyone knows about the absurdly high A-level grades that even third and fourth-rate universities now command.
And yet, and yet . . . Both my husband and I were star pupils at school, forever anxious to get top marks in everything, but in many ways it did us more harm than good. Real life isn't an exam, you can't ever pass it (only pass on from it), and knowing what we know now, we'd both gladly trade in our bundles of exam certificates for a few more ladlefuls of the stuff that really counts - confidence, social skills, a keen sense of purpose and the grit to hang in and get there.
Because of this, we deliberately try to encourage our children not to take school too seriously and to look critically at any system they find themselves in. After all, what's an exam, we laugh carelessly.
But the result, to be honest, is just a mish-mash of conflicting messages. What's an exam, we say. But when the low marks come in, our brows grow thunderous and we start to fume and steam. Aren't you ashamed of yourself? Are you happy about this? Is this really the best you can do?
What we want, of course, is to have it all ways. Achievement without effort. Careless honours. Results without sweat - particularly our own, parental, sweat.
Deep down I know the answer to this question of how far parents should be involved in their children's work - and it isn't a comfortable one. Parents shouldn't sit shoulder-to-shoulder with their revising teenagers, or run around after lost physics books, but they should do more than let loose the occasional yell of "turn off that television while you do your homework!" They - we - should be the ones nurturing our children's confidence, nudging them towards self-discipline, encouraging them to take pride in their work, and helping them to discover their own true talents and interests.
But all that takes not just time, but real thought and effort, not to mention persistence, forbearance and (dread thought) teaching by example. And who has time for all that?
Much easier, when you think about it, just to work up a sweat about exam results. And let real life take care of itself.