My own view, for whatever it’s worth, has always been that expressing a view as to #1 choice is pretty meaningless in the process, except in very limited circumstances. If you are an athlete being heavily recruited to be a started at a very specific position (i.e., QB on the football team, goalie on the hockey team), then that’s a whole different thing – there, the coach needs a starting QB for the next year, and if you might be that person, then he needs to know whether you’re going to come or not, because otherwise, he’s got to push for the kid who’s second on his list, etc. I also think that siblings fall into a different category, because they should already know enough about the school to make an informed choice. But otherwise, I don’t think you have any particular obligation (implicit or not) to make a first choice, or to communicate that. Indeed, I think that most schools would really prefer that kids come to the revisit day and make their choice after that, so as to optimize the likelihood that kids will pick the school only if it’s the right fit.