|I BELIEVE I CAN FLYYY|
The experience gained from falling is tied directly to damage done by the fall. Each half heart of damage earns 120 XP from a fall with no roll, or 80 XP from a fall where a roll or graceful landing was executed. Damage before the roll/graceful landing damage reduction is used to calculate the XP, gain. If the fall is fatal, no XP is earned.
Because a player has a maximum of 10 hearts of damage, the maximum XP you can earn in a single fall is 2280 from a height of 23 with no roll or gracefull landing, or 2640 from a height of 36 with a graceful landing.
Currently, a fall with feather fall/protection armor equipped will net the same XP as if you didn't have the armor on, but without suffering the full damage. Because of this, you will also earn no XP for a fall that would have killed you if you didn't have this armor equipped.
Another key thing to note is that in vanilla Minecraft, you take 2.5 hearts of fall damage whenever you use Ender Pearls to teleport. This fall damage does apply to Acrobatics XP, and the XP gained is calculated with the above formula, resulting in (5 * 120) = 600 XP.
How to get ExperienceEdit
One way to automatically farm acrobtics experience is to create a redstone elevator. Using this, you can be quickly transported to the top and dropped down. If you have the materials, consider adding a dispenser at the bottom for instant healing, as this activity will drain your health quickly. Beacons with regeneration are also an option.