According to the local Yamaha shop the 6310Z is still available - fuzzy-felt said it is discontinued - However your brass/trumpet teacher should be the person to get assistance from. My son uses a Yamaha YTR 4355 and plays regualy in a Jazz Band, he has used this for two years and is v. happy with it. (appx 400 pounds sterling)
The weight of the trumpet is important also as I dont know how old you are as 10th grade means nothing to me in England if you are young the trumpet gets heavier and heavier as you play and you struggle to keep the bell up after a couple of hours practise/play.
The Yamaha Xeno is expensive (1,500 pounds sterling) but has a great sound !

This is the one my 40 year old husband recently got and boy it rocks!