So first it was set at 10k wp
then it was reduced to 400 wp
now it's at 1500 wp.

The best solution is not to go by wp, but instead by how much experience a player has received in the different game modes.

For instance, there should be a checklist of different things (kills, hacks, etc) that you much accomplish before you can proceed into normal matches. It was already proven possible by the event that CCP held a while ago that tracked how many kills, kill assists, hacks, and installation destructions a player got.

My idea is that hopefully this will give players a sense of accomplishment, and help new players figure out what to do in the beginning. This method also solves the problem of players who are slower at learning the game and still need some time to practice, vs players that are well experienced and want to get into the main game right away.

This is my suggestion of what is required to graduate:
-50 kills (2500 wp)
-10 obective hacks (1000 wp)
-25 installation hacks (1250 wp)
-25 team bonuses (assists, triage, revive, guardian, 750-3000 wp)

To make sure players graduate the academy, they will automatically be released after they have gained a certain amount of wp (say something like 10-25k wp) or when they have accumulated 2 million sp.

I like the idea, but we need to address the elephant in the room. No matter what happens with the academy, it can't be used as a replacement for proper tutorials, a better overall new player experience and matchmaking. The way thing currently are now, the academy is just a little safety bubble before newberries get thrown to the sharks. No matter how long the duration lasts, players that barely have any idea what to expect from this game are going to continue to be thrown in matches with experienced players with 10x the amount of SP they have and are going to get driven away because an integral balancing mechanic wasn't a top priority.

It's like CCP just looked at every other FPS and thought "they don't have tutorials, I guess we don't need one either"