Back in 2012 I read that Duncan Lunan had written a book about the Green Children of Woolpit but hadn’t been able to find any folk songs about them. As one of my songs, Child of Green, is about exactly that subject* I got in touch and, to shorten what is a long (though fairly interesting!) tale, the upshot is the sheet music and lyrics to Child of Green have now been published in the first Children from the Sky annual. 
You can read more about the annual and Duncan’s research into the Green Children, as well as order a copy of the annual, on the Children from the Sky website.
*you can hear it by clicking the “songs” link which will take you to my bandcamp page.