you might Google "astral schools in wizard101"....I did and found out a lot....each school was explained and how each would benefit your wizard....then you decide what will help you down the road.
At the level 50 bracket the only Astral Spells available to you are Strong & Keen Eyes from the Sun School, Fortify from the Star School, and Polymorph Gobbler from the Moon School.
My personal recommendation is to stay away from the Moon School unless you just like the fun of it. It's harder to master the Moon School spells because you have to change your whole strategy in order to utilize new spells that come with each Polymorph. You lose your entire deck of spells while you are in this transformed state.
If you and your friends are planning on always questing together then here are my suggestions for each of your schools:
Your Life wizard would do well to train in a few Star School spells: Fortify because it shields your wizard from 15% damage during attacks for four rounds. It's like a universal Tower Shield with a fraction of the resistance but able to be utilized for a longer period of time. Infallible is great for the same reason above because of accuracy. Vengeance if you really like those extra critical hits/heals but it's not utilized so much later on when you get Mend and Cycle of Life however, it works on both heals AND hits. Empowerment is favorite of mine no matter what wizard you have. It allows you to gain a pip when you get hit with ANY spell rank 4 and higher including heals!
The Sun School spells I would train are: Keen Eyes (it's line of accuracy spells) is a great spell to have for your heals. The last thing you want is for a Satyr or Rebirth to fizzle because you have an inaccuracy charm, especially when you need it most! I also love the Strong line because there will be instances when you won't have your friends in battle and that extra damage helps!
For your friend's Balance Wiz I recommend also training in the same Sun & Star spells as your life wizard because they DO have heals that are important and the fizzle rate on balance seems to be as high if not higher than Ice wizards (my experiences anyway). You may also think about Amplify also
for both your Life and Balance wizards to go along with the Sun strength spells just to give them that extra oomph when hitting.
Your friend's Fire wizard should definitely work with the Sun and Star spells that will increase damage output (never can have enough, right? LOL) mostly because they are the hammer (heavy hitter) in your group. This friend has your Balance friend to set them up and you to make sure they stay healthy so their primary function is to take out the enemies. The Strong line in the Sun School is the most likely way to go no matter which wizard class you play with. Since Fire doesn't fizzle as much (with good gear) as Balance or Ice (even though Fire has lower accuracy on it's spell cards), it's not necessary to train in the Keen Eyes accuracy line from Sun though they can if they wish to.
For Star School advice mine is to train in Fortify for those solo battles since health is lower. It's up to your friend though whether they would rather take the chance on increasing criticals with Vengeance or the certainty of increased damage output with Amplify from Star auras.Of course I also suggest Empowerment only because the later worlds you rely more on Dragon than just Meteor so the extra pips come in handy.
Hope some of this information helps you and your friends. Any of the later Star and Sun spells you get in Zafaria and Aztec will depend on how you train in Celestia. By this time you should be somewhat comfortable knowing which ones work for each of your wizards and what you wish to continue in.
