Hi, unfortunately I'm not yet a current Culford parent so can't help in that respect, but I was at the school for 5 years (including during the infamous cannabis-gate... which, of course, was ridiculously overblown by the Sun newspaper and thus I find it quite amusing that people are still talking about it!!). Believe me, having achieved 4 'A' grades at A-level, and being one of 6 Oxbridge entrants from Culford that year, I came across infinitely worse drug habits amongst Old Etonians and even Old Ipswichians at university than we'd ever seen at little rural old Culford!!
Anyway, my experience back then was that I couldn't have had a better education for me. All of this stuff about it not being very academic, etc., is relative to the fact that it has an academically diverse intake (its ethos as a Methodist school necessitates this) and that it's in an essentially rural area (statistically the large town ex-grammars like Ipswich always do better on grades alone). Look at the 'value add' for individuals, rather than the headline grades (although I note that last year they got better 'A' and 'A*' grades at A-level than Ipswich! - en.wikipedia.org/wiki/Culford_School#References).
IMO, having been to university with many products of the supposedly more 'academic' schools in East Anglia, knowledge isn't simply about reading books and cramming exams. Many of those products seemed to be a little two-dimensional and, in many cases, completely odd! So, to me at at least, the diversity of the community at Culford is an asset not a hindrance (and I can assure you that my parents most certainly didn't have low aspirations for me! - that's why they took me out of the state system after middle school). If your DS is bright and prepared to grasp everything on offer, then he will do well. The sport seems to have come on leaps and bounds as well - I note that the girls hockey team have just played in the national finals and that they've got an England rugby player on the books.
There were some excellent teachers at Culford who taught us to think in the broadest sense, and the grounds and general atmosphere are really quite inspiring. There was every opportunity to become a fully signed-up member of the human race at the school, and it's notable that we still remain a close-knit community of friends (many friends from uni and work comment on how friendly everyone is - the school definitely doesn't produce the aggressive or pretentious public school stereotype!). Reading through the alumni newsletters, etc., that we're sent, it would seem that they have record pupil numbers and that boarding places are full (it's roughly 50:50 boarding and day BTW, and very well integrated) - so I'm glad to say that it's not just us who think it's a great place to be educated!
Best of luck and hope the visit goes well.