I'm not sure what PTL stands for...last time I saw it, it was Jim & Tammy Faye's Praise The Lord show. I hope it doesn't involve all the mothers putting makeup on with a trowel.
PTA is a specific organization, also sometimes known as PTSA. If it starts "PT" and ends "A", it's the PTA. If it ends "Barnum", it's a circus. If it ends "Cruiser", it's a car. Just about anything else is a parent-teacher group that is not affiliated with the PTA.
Non-PTA groups can choose whatever name they want, and some may choose a specific designation to express some underlying philosophy. There was even an on-line poll here last year about what names different groups choose.
Hmmm...PTL...Parents-Teachers-Librarians?