I know that you get the quests at various points in the storyline, so maybe you just haven't gotten far enough in the story yet, I'm not too sure, but this probably belongs more in Halston's Laboratory or Azteca, rather than the Dorms.
The astral school quests in Azteca are only available after attaining specific levels and unlocking specific areas. To provide more details:
Access to the first obelisk which is the school trainer is only unlocked after you achieve level 84 and complete the quest given by Pacal Redmask in Zocolo. Note that this quest requires you to face three enemies (one being a boss) at once and is a solo instance; meaning, no one will be able to assist you. So bare this in mind and prepare adequately.
The school trainer (my personal favorite) is given by the same NPC mentioned above however, it's criteria is a little different. As expected, the quest is only given when you're at least level 86. Similarly to the School quest, this quest also requires you to face three enemies (all including a boss) at once.
The final trainer, the is unlocked at about level 88 and after enough progress is made in the location Pitch Black Lake. It will also pose a little bit of a challenge as well.
There are several requirements in order to get the astral quests. First you need to have done the astral quests in Zafaria Bungle in the Jungle through Midnight Sun given to you by Inyanga Whitestripes in Baobab Crossroads at level 64. Second, you need to be level 84 and completed through the quest King of Fang and Claw in the storyline quests for Azteca. This will unlock the astral quest for the star obelisk in Azteca. Once you reach level 86 and have completed through Thorn in my Pride in main story questing in Azteca, you will be able to access the astral quest for the sun school. When you are 88 and have completed the quest In my Eyes, the moon school quest will become available to you.
First, this is a problem. It should go into the Halston's Laboratory section. Second, you need to be level 85 or 87. Sorry I don't remember the particular level. I also think you need to cross a landmark in the story line.