As part of our club tenancy arrangement with our college landlords we teach anywhere between ten and twenty 14 year olds every Wednesday, the basics of how to shoot, safely. We concentrate on FT and HFT type shooting, where rangefinding is important, not ten metre or indoor stuff where the range is known.
I would say the majority of the kids that come to us really don't have much idea how long a yard is. It's hard enough teaching them aspects of range estimation in a unit they are familiar with, but we have to begin by comparing yards with metres.
Sooner or later we're going to have to think in metres.
And I would support a minimum target distance of 10 metres too.