In reply to Denni:
I don't normally get involved in these typically blinkered, ranty and prejudiced UKC posts, but as the other half of a multi horse owning partnership, who also occasionally rides, I'd like to offer the following comments:
Horse droppings on roads can definitely be a bone of contention, particularly in urban areas where townies are concerned. For country dwellers, who also have to cope with cow shit and sheep shit on the roads, it's an issue which is kept in perspective. It's not illegal for a cow, sheep or horse to shit on the road in the UK, nor is it a legal requirement to pick it up.
A droppings bag can be fitted on to carriage horses, but this is not possible for the ridden horse. A major issue is that it is virtually impossible to predict when/ where a horse will defecate although it will be particularly likely to do so if startled or at a place where it has been startled before. This could explain the droppings outside the school as it's likely to be a situation that would cause great stress to the horses and possibly the riders (horses can sense their rider's stress and can become agitated and nervous as a result.) It may well be the case that the riders in question should think carefully and try to avoid riding where droppings are likely to give offence or time their ride to avoid busy periods when their horses could be needlessly startled .
Confrontation and shouting as described will only make the horses shit more out of nervousness. In any case, contrary to popular belief, horse shit is just accelerated compost and droppings from healthy horses pose minimal risk to human health.
In many cases, people who have no understanding of horses wish to see riders dismount and shovel the shit into a bag and take it with them, just as you would do with a poodle on a lead. While this may appeal to both the ignorant and the uninformed, such action is often totally impractical as a dismounted and riderless horse will always pose a great danger to the public because if it was then startled, it would simply bolt uncontrollably. There are also issues with remounting an agitated horse who won't stay still on a public road as car drivers usually drive far too close, too fast and too aggressively to horses these days. The very last thing most riders would want to do is deliberately dismount a horse on a road, then leave it while they go and shovel a pile of shit into a bag. Tying the horse to a fence or similar isn't an option, just in case the horse might injure itself - or others - if startled while tethered.
People make choices; sometimes they're the wrong ones. What's needed is mutual understanding and tolerance on all sides, something that's sadly lacking these days, as evidenced by your response, the mother's stupid actions with the car as well as the horse riders' equally stupid decision to ride past a school at a very busy time of day.