The pieces are in their original keys, and have been chosen to cover all 12 major scales, moving around the circle of fifths. Each primo part presents at least two ascending and descending runs of the scale.
In case the teacher is not available to play the secondo part, or as a practice aid, recordings of all of the pieces are available online, at lauraspitzer.com. There are two sets of recordings - one set with both parts being played, and another with only the teacher's secondo parts.
Here's a sample:
Although this book is written for pianists, I can certainly see a way to adapt it for other instruments (like the ones I teach, clarinet and saxophone). It would be easy enough to use the online secondo recordings, and ask the student to transpose the primo parts as appropriate for Bb or Eb instruments. This could serve as a lesson in transposing from concert key, and shouldn't be particularly hard for students, since the primo parts move scalewise. For violin or flute, no transposing would be necessary!
Scaling New Heights is available on Amazon - just click the link. For more about the author, visit lauraspitzer.com.