Hi all - newbie here...

This question has come up in a fan forum for singer songwriter Grace Vanderwaal, who at 14 yo wrote a song for the Disney movie "Stargirl".
The question is - is she the youngest person ever to write for a soundtrack, and who else under the age of 21 has accomplished this feat? any comments of a general nature are welcome, and I hope to introduce people further to Grace - seems she is not known here.