I do a little bit of practice in going in an outline, bending and basic transitions with my youngster whilst hacking as she is not really mature enough to be schooling properly. It works well for her as she (and me!!) is in a much more relaxed and willing state of mind on a hack than if we were in the school/field solely for a schooling session
I school when i hack. I pick a specific bush/tree and trot canter till exactly there trying to stop at exactly where i picked. I will leg yeild back and forth across the tracks. Take an "inside" bend then change it, then go straight ect when walking/trotting/cantering. Im sure others will have more ideas too
Leg yielding works well - out to centre and back if roads allow. I agree that with youngsters 5 minutes out hacking is a good way to school. In all honesty though I just let mine relax now he's older.
Yes I school whilst hacking, I have found it very useful to teach leg yield and shoulder in/fore (very useful when a horse eater in the hedge!) plus using it for collecting and extending esp in the walk as really thinking forwards.
i do all my schooling on a hack - i find a big open grass field and work in there for about 20mins - in terms on stracks etc - i do lots of transitions - perfected walk to canter and trot to canter on both leads on a stright line by working on hacks
I used to do nearly all my schooling whilst hacking (not entirely through choice as I had no access to a school growing up). Exactly the same work as in a school really - lots of transtions, lateral work across tracks if safe and ground permits. It's a good chance to get a horse really working forward as they often retain more interest whilst out and about but it is very important to make sure they are just as off the leg and generally attentive as you would ask them to be in a school. Best bit about hacking though is that you can make the most of hills - good, forward moving walk and trot in a really steady, consistent rythmn, both up and down hills - absolutely invaluable for getting horse really using himself and for building the right muscles!
Definitely always school when out hacking as others have said lots of leg yeilding and shoulder fore, up and down transitions and my girl always goes out in a contact, though if we are going for a bit she does get to work on a long rein too. Find it really helps as they are often more relaxed on a hack as am I so can work on specific stuff without getting stressed and blocking, plus if they really begin to listen to you and leg aids etc when out on a hack find it much easier to deal with when confronted by 'monsters' on the road especially flexing to keep them calm and listening and convincing them that you are not about to let them go past something that is about to eat them!