Primary staff and parents often chart children's growth by making chalk marks on a wall. But there is some bemusement this week at an Assembly government drive to establish the height and weight of the nation's young compared with those in Europe.
A pilot scheme in seven local authorities will take the vital statistics of selected reception and Year 4 pupils and compare them with those outside Wales.
If successful, it may be extended across the country. But some teachers were perplexed by the mass data collection exercise.
Andrew Strong, head of Llanbister Primary in Powys, was surprised when an official turned up unannounced at the end of last term to discuss the programme.
"Are pupils in Wales heavier, lighter, taller or shorter than pupils in France or Belgium?" he asked. "Why does the Assembly need to know this? I presume it's in the interests of children's health?"
Project co-ordinator Dr Ciaran Humphreys, consultant in health intelligence for the National Public Health Service for Wales, said some children were already measured when they started school but there was inconsistency in how and when measurements were taken.
Children in Europe are already measured and weighed at four, but the Wales trial will also include seven and eight-year-olds.
"We have had a positive response from local education authorities," said Dr Humphreys. "Many areas are introducing healthy-living schemes and this is one way of testing whether they are having an effect."
The data will be used to examine trends in growth, including obesity. Wales will also be compared with England, where there is a well-established programme of child measurement.
Latest figures from the World Health Organisation show that Wales has one of highest numbers of overweight teenagers in Europe; only Greece and Malta fare worse.
This month, the Assembly government launched a national obesity scheme to tackle the problem.
The data will not be used to identify particular pupils who should lose weight, but severely underweight children are likely to be referred to dieticians.