The trouble was that it took time for them to learn that horses can have minds of their own - they are not like BMX bikes or motorbikes - and sometimes exercise that prerogative, particularly when they know they are being ridden by inexperienced riders.
Now few people know this, but one of my sidelines is horseriding. Each year, I run a horse-riding business for a couple of weeks for a friend of mine while he goes on holiday. Some years ago, I rode a horse from Offa's Dyke to the Welsh coast, six days almost non-stop in the saddle.
So when we went pony trekking, I often acted as an extra guide: youth work(er) on horseback. It can be a real learning experience for young people. The high spot, until new regulations forbade it, was a brief canter across the top of the moor. The real guide and myself had a cunning arrangement to separate out those who were capable of the canter and those who were not. He would ride on to the point where the canter would finish. I would stay with the group, most of whom expressed a wish to canter.
I would double-check their enthusiasm to do so and ask whether they felt they were fully in control of their mounts. Of course, they said yes. But as soon as the guide walked on, many of the horses followed. The young people riding them complained that they could not hold them back, at which point I would suggest that perhaps they were not yet ready to canter. It was a moment of disappointment, but a lesson that skills can only be learned incrementally.
But occasionally somebody would slip through the net of this cunning plan. He (usually he) would take off on the canter, only to find that his horse would not stop, or at least not appear to be stopping. Panic would set in, although it would eventually slow down. The panicked young person would dismount, unsure about going on. Releasing the reins, the horse - now fired up - would seize the opportunity and run off.
In my ancillary role, it was my job to stop it and bring it back. So even that aspect of Scouting for Boys is perhaps not completely out of date.