I agree with Wonderwiper ~ this is my same approach DURING their child's time here I maintain a friendly demeanor during drop off and pick up but keep a professional 'distance' from clients in regards to socializing outside of work and just politely arrange to respond to invitations with 'Oh that sounds like it would be a lot of fun but we are previously committed' and than once they are no longer 'enrolled' if they continue to want to be friendly and invite me to something social THAN I can feel free to attend because the business relationship has now ended and it is easier cause no need to worry about the crossing of the two relationships ... it is the same with I never 'friend' any of my current clients on Facebook or other social media and actually use a different variation of my name on those sites so it is very hard to 'search' me but if they ask me AFTER as a way to keep in contact than I will find them and friend them.