Craig writes: PTOs (parent-teacher organizations) are independent parent groups not affiliated with the National PTA. About 20-25 percent of schools have PTAs. The rest of the parent groups are independent. PTO is the most common acronym, but there are many others: HSA (home and school association), PTC (parent-teacher committee), etc.We use the term PTO in two ways. Because it's the most common acronym, we often use it as shorthand to refer to all parent groups (including PTAs). At the school level, PTOs and PTAs do the same thing -- build the kind of supportive community where teachers and students can do their best work. We also use the term PTO to refer to all independent parent groups -- in other words, all groups except PTAs. Hopefully how the term is being used in each case is clear from the context. For more on the differences between PTOs and PTAs, see our PTO vs. PTA page.