Gossip about schools dates quickly. Heads usually move every 5–10 years and there is a complete change of pupils every 6 years or so. So there is continual change, apart from any major changes (such as introducing the International Baccalaureate or becoming co-educational). But reputations can live longer (‘the school where the first eleven torched the cricket pavilion’). So treat grapevine information with caution.
A parent with a child currently at the school can give you contemporary low-down but their view of a school will be coloured by the very personal experience of their child − which may or may not be relevant to yours. Prep school Heads should be up-to-date and may be more objective than parents.