I'm really interested in this issue. WE have been to three schools, one comprehensive, one state grammar (in the top 50 academically) and one independent (also very academic).
The comprehensive did an evening visit day but we also went during a normal day; the indie did a Saturday open day; the grammar, lots of visits during a normal working week.
The grammar gave the strong impression that it wasn't a priority to show people round or engage them. Which in many ways is commendable: they're saying a. our results speak for themselves, b. we're busy teaching and c. we don't actually need you, since we're very oversubscribed and competitive.
But you know what, it REALLY pissed me off. The point was by making the assumption that all we cared about was the results, we didn't actually get to speak to ANY of the teachers. And since teachers (and teaching) are, for me, by far the most important bit of the school, I found it incredibly irritating.
The local comp (which is no slouch academically, given the diversity of the population) was so much more interested in talking to parents AND prospective pupils. And that is what I am going to want from them throughout the time my kid is there, not a kind of paternalistic 'we know best, just let us get on with it' approach.
We have decided, after MUCH angst, that the local comprehensive school will be best for our son. Even though he is obviously a GENIUS and could walk the entrance exam with his eyes closed.