The jazz ensemble warmup is a great opportunity to teach some scales that are useful in jazz improvisation. Common modes like mixolydian or dorian will help get the players moving around their horns and will also give them some basic improvisational tools.
If at all possible, choose scales in the key or mode of one of the pieces you plan on rehearsing.
Printed scale exercises are available from a number of sources. The warmups in the Standard of Excellence Jazz Ensemble Method include all the scales used in the charts for the method, as well as the related arpeggios. First Place for Jazz takes players through major, mixolydian, dorian, and blues scales in three different keys.
These activities warm up the fingers and prepare the ears for what is coming next.
Ear Training and Internalization
In place of reading, another approach is to teach the scales or chords by ear alone. While this process takes more time, the scales become much more internalized. Begin by teaching the root of the scale or chord, and gradually add more pitches until the students know all the relevant pitches. Depending on available rehearsal time, you may wish to add only a note per day or only two notes per day until the entire scale or chord is learned.
Putting Scales and Chords to Work
Apply what students learn immediately by having them improvise with the scale, chord, or with the notes that they know. This can be out of time, or your drummer can add any kind of groove you or the students choose!
Do not neglect the rhythm section. Guitar, piano, and bass can do this exercise along with the winds. Drums can either play vibes or another mallet instrument if they are not playing different grooves under the scale exercises.
Make It Manageable
Remember, you don’t have to learn everything in all 12 keys in one rehearsal! Keep everything bite-sized and take the long view. Persistence is key. Be creative and have fun!