I've met quite a few ex-riding school horses and generally they're had problems.
Like eml said, they are used to be handled by confident, professional horsemen and don't have the oppertunity to mess about and be bad-mannered - they just don't bother as they know it's not going to work. They are ridden under constant supervision and have a proper 'job' to do with a set routine.
When they go to a private home they often no longer have that rock steady pillar of rountine and confidence and some find it hard. They have less work, there's less routine to it and they often have the oppertunity to to take the micky in a way that would be quick quashed in a RS.
However, I suspect a lot of the problems are because NOVICES often buy ex-RS, in the assumtion that as a good safe RS horse, they will automatically become a good a safe private novice horse. Unfortunatly said RS horse gets home, takes one look at their novice (and often nervous) new owner and rubs their little hooves together gleefully think about all the mischeif and P-taking they can get up to
Others find it stressful not having that steady and comforting 'job' and rountine and become 'naughty'
If they were bought by experienced, confident riders, they might be much less hassle (or any slightly bad behavour is quickly sorted before it esculates), but that kind of rider usually doesn't want a ex-riding school horse.
