Well, in the States, it's more like a 100m, usually -- if you go to all the trouble to buy a My Little Pony (or Peter Lynn Gecko) kite, you don't want to fly it so high that you can't see the details. read more
Usually kites fly in the range 50 - 400 ft above ground level. Beach flying usually has the benefit of steady winds so kites can be flown at lower altitudes without crashing. In areas with trees and buildings, winds are often turbulent so a kite has to fly higher to be in steady winds. read more