Playing higher on Alto Vs Tenor trombone?

"Will I be able to play higher on Alto trombone than a tenor trombone with the same mouthpiece?" asked my student. Well, let us discuss that. Your buzz determines the note not the horn. The mouthpiece isolates muscle groups in your embouchure that optimize the frequency that you can build your strength to play at. If you don't have the strength to play high on a tenor trombone, then you won't find any distinguishable range increase on the Alto trombone. The range you currently poses will "slot" better and the sound will be cleaner which makes it easier to play but not easier to play higher than you already can.