Look to the future and remember your new horn will never be worth more than you pay for it new. There are just too many used saxophones out there now.

I myself would stich with the Yamaha

First of all, you do not say what type of horn (sop, alto, tenor etc).  That information greatly helps the responders.
Secondly, I will probably get flamed for saying this, but I do not consider the Cannonballs to be professional horns yet (the key word is yet).  And my reason has nothing to do with tone, but a professional horn is well built and holds up over time.  Cannonballs have been out for awhile, but I am not sure it has enough history yet to show how well it will last.
Since you are buying this for high school, I assume that you may not be fully developed as a player.  As you gain more experience, you will find that the tone you get is more dependent upon mouthpiece, reed and neck than on the horn.  Therefore I recommend that you buy a solid pro level horn with good history, and that can be serviced by most technicians.  I would consider the Yamaha 62 series pro horn since they are a bargain when compared to the price of a Z or EX.
If you decide to major in music in college, you may find that certain programs encourage the use of certain makes of saxes, so don't overinvest at this time.