My friend works in statistics and research where she covers infection control and disease outbreaks. She told me from where she's sitting, there are fewer d&v outbreaks in private schools.
(This is not official research, just something she has observed.)
She thinks it's because parents don't think twice about keeping their children off an extra day if they are ill because they don't get penalised and because private schools generally have more money to do a regular deep clean and educate and enforce kids to wash hands after toilet and before eating.
Does this sound like bullshit to you?