This is a awesome XP farm and you get XP really fast. You also get tons and I mean tons of ender pearls in the minutes I had over 3 full stack of stacks of them. I made it in the xbox edition. I hope you enjoy.
I can't really tell you how many blocks you need because it varies on how big you make.
First you need to light up the entire end I know this sounds like a lot and it is but otherwise it won't really work it will take a long time but trust me it is worth it. Then go to one side of the End and make a glowstone bridge with iron bar railings or fences whichever you choose to about 15, 16, blocks whatever you choose.
Then make a platform next to your bridge that is 2 thick and 15 long and too wide. Now put sticky pistons over on top of the whole thing and put glowstone on them. Now put quartz or your choice of blocks and put them on the sides of the piston. Put red stone all the way along those blocks that you put next to the piston. Now build what you see in picture 4 on one side.
Put redstone torches on the 2 blocks that are on the sides of the Pistons look at picture 1. Now put redstone on the two blocks in between the two charges. And put a block in front of one of them and then one to the side of it like you see in picture 3. Now put a repeater going into a block next to A redstone torch like you see in picture 4 then put a redstone on the block behind the repeater then put a block on that redstone and on that block place a lever.
Now place half slabs all around the glow stone. Now go up exactly 43 blocks not one less. One more. Now make almost like a big rectangular box.
Go back to the bottom and break off the first two blocks that connect the box to the half slab. And then place a row of blocks connecting those. Then every 2 blocks going up to the top place a line everywhere so that Endermen can't spawn there. When you get to the top the top line should be 2 thick.
go to the top and place buttons on both sides. now go up 2 blocks and on both sides and place vines on them.
Next to the block that has a vines on them go to the side and build what you see in picture 1 placing pressure plates on the same block as the top vines and on every other block place a repeater leading from the pressure plates to the block in front of them. Place redstone in between each of the repeaters. On the block in front of the repeaters and redstone place you're are sticky pistons. Now place a block in front of them.
Now go up to blocks and repeat step 8. You need to repeat steps 8 at least two more times the more times you repeat it be better.
Now go to the side by side next to each pressure plate and make a row and of blocks for long and put half slabs on them so Endermen cannot spawn there. Now go to the top and we are going to cap it off by putting blocks 2 high above it all over the top then putting half slabs all over it.
Now go back to the bottom and watch the Endermen fall. The reason you put the switch is win is because when the switch is flipped up and the pistons are up the Enderman will fall and not die so that you can hit them with one hit and they will die giving you XP and ender pearls if you flip the switch off the Enderman will fall and die completely leaving just ender pearls. I hope you enjoyed this instructable. Don't forget to vote.