Just don't let the parents in your house. I make it very clear using my body language and my position between the front door and the rest of my house that parents are NOT welcome to come in at drop off or pick up. This is not playgroup, as playfelt has mentioned.

Besides, I do not allow ANY parent in my home while I am caring for the kids. I don't know WHO these people are. Where are their clear police checks? And, where is their liability insurance if it is THEY who harms a kid on my watch??