I teach in a grade 5-8 band program with about 1/2 of the students as beginners. We have worked through the Bb, Eb & Ab scales.
I usually do a multi-task warmup.

1) Breathing excercise.
2) Scale (what ever scale we're working on), first in whole, then 1/2 then 1/4. Then 1/8th. The kids usually want to challenge themselves and try to play it faster.
3) A short chorale. Then we tune & play the chorale a 2nd time.
4) A part of my board has the pyramid & reverse pyramid written. All I have to do is make the shape with my hands & the balance comes into line.
5) This is done within 15 minutes. We then focus on the performance music or articulation stuff.
6) While the winds warm-up, the drummers work on snare rudiments on their practice pads.
I've long been an advocate that grades 5-8 aren't slow or dead. They can do many of the same things as high school groups-you just have to push them and focus them.