Here are some scores that are useful for basic practice.
The following is made for junior high school band, so elementary school students should choose and use only the parts that are easy for them.
(All are PDF files)
Scales and Arpeggios in fifth. A
Scales and Arpeggios in octave. B
Interval Lip Slur for Band
Scale of Thirds Scale of fourths
Scale variation 1
Scale variation 2
Scale variation 3
Scale variation 4