Not so much school groups, because you tend to have someone going “Okay, everyone, the drummer hasn’t turned up, so instead we’re going to…” or similar. In church groups, they tend to be overly optimistic: everything will work out, because it’s all in God’s hands, and if we DO make mistakes, well let’s all remember that we’re serving God and not giving a concert, so no-one will mind. It means you’re not nearly as prepared as you actually should be.