Magpie (a fine duo) have two albums out with songs that you'd probably find useful. You didn't mention the age range you'd be working with in your school visiting, but a lot of their stuff is good for both the upper and lower endss of "school age". One of the albums is called "Living Planet"(1990), the other is called "Circle of Life", and I think it would have a lot of exactly what you probably need. Particulars are at www.magpiemusic.com.