Westlife were a better band than the Velvet Underground. Don't laugh. They were. Look at the evidence.
Westlife: 14 No 1 singles and 50 million records sold. The Velvet Underground: didn't have a single "hit" until 20 years after they broke up, when Venus in Furs crawled to No 72 in the charts on the back of an advertisement for Dunlop tyres.
It's a ridiculous argument, of course. Westlife traded in aural mush that was about as enduring as a snowman in the desert, whereas Lou Reed et al should be measured by their huge influence rather than the units they've shifted.
But similar fallacies come into play with school league tables, the latest annual round of which was published in the newspapers last month. These are not only a blunt measure of success; they also lead to great schools being shamed and below-par schools being lauded.
Imagine the staff of School A in a poorer part of the country who, driven on by a fierce belief in the potential of even the "worst" pupils to progress in life despite myriad obstacles, help children to do far better than anyone expected when they traipsed into S1.
Then the league tables are published and School A is languishing near the bottom. Meanwhile, School B in the well-heeled suburb up the road, which everyone knows could be doing a lot better for its pupils, can bask in the glory of a far higher chart position. How dispiriting is that?
Conventional league tables tell us little more than the demographics a school is dealing with. For some pupils, a National 5 would be a great achievement; for others, four As at Higher may feel like failure. A simple tally of exam results is meaningless without knowing more about who sat those exams.
And it is not just teachers who complain about misleading interpretations of a school's success - employers do, too. "We should stop measuring schools on qualifications," David Watt of the Institute of Directors told MSPs late last month (see page 10). If there had to be league tables, he said, employers would find it far more useful to know how successful a school was in raising literacy than how many exams its pupils passed.
Yet old assumptions about education die hard. At the same meeting, Iain Ellis of the National Parent Forum of Scotland pondered the attainment gap between rich and poor. "What gap are we trying to close?" he asked.
He suspected that for all Curriculum for Excellence's rhetoric about more sophisticated notions of educational success, Scotland still wrongheadedly ranked the pathway to university above all others.
Which brings us back full circle. If bridging the attainment gap becomes largely about getting more children from poorer areas into university, then it fuels the damaging myth - equally applicable to schools and pupils - that leads to league tables: that the more qualifications you rack up, the more successful you are.