Originally Posted by minstrel
In the UK it's considered correct to show in jodhpur boots with jodhpur clips if you are under sixteen (a junior), And in tall boots as an adult (sixteen and over). The Pony Club tends to be pretty strict on anyone competing for them, and some more prestigious shows can be. However you will always get juniors who do show in tall boots (usually in dressage/ eventing, but some in showing too). However that's UK dress code.
I'm 20 and am in the UK and I only just got tall boots. I only do fun non serious shows/comps though so there's almost no rules apart from smart looking. I still wear jodhpur boots in spring/summer for normal riding. I think most of the pony club kids at my yard do show in jodhpur boots though from the photos in the office.