I did the Winchester/Romsey/Chandlers Ford secondary trawl a year ago, selecting a school for DS1- and here are my opinions!
Kings: An amalgamation of 2 secondary moderns. Felt very much like my grammar! Smart, strict uniform; rigorous streaming in everything (A1,2,3,4; B1,2,3,4: C1,2 etc) Guess the DCs know exactly where they stand!! Big catchment, largely fields so not impossible to get into from a fair distance away. Bit of occasional hassle where the 'posh' kids and the kids from the huge Stanmore council estate disagree (that's from the mouth of an ex-head girl!). Good GCSE results.
Westgate: Ex grammar- you have to live in catchment, which is very liberal, middle-class Winchester. 2 separate lots of friends who live in this catchment chose Kings for their DSs as they felt it might be too arty and liberal for them. Pretty good GCSEs and well rated by those who attend.
Henry Beaufort: Didn't visit, work with many who attended: Say it's perhaps the weakest of the 3 secondaries, but still fine by national standards.
Mountbatten (Romsey): Very pleasantly surprised. Recent new Head who is sorting out a few discipline issues the school suffered from, as a result of many of the northern Southampton secondaries being SO BAD a lot of DCs arrived at MB from N. So'ton who weren't really 'school ready' if you get my drift. Good friend's DD there, very happy, DD and mum. Reasonable GCSEs. Lovely site.
Romsey Community : mm. I have never liked the school, I tried as it was DS's junior school's catchmented secondary but it's scruffy and seems hell bent on crackpot educational ideas like setting Y7's adrift with 4 week single subject 'projects' to do as homework with no structuring whatsoever- Lots of tears and that's just the mums! Adequate GCSEs
Thornden (Chandlers Ford): OK, I'm biased as this is our chosen school. Strictly catchmented, big (1400 Y7-11) BUT it is a proper comprehensive yet actually produces the best GCSE results in the county for non-selective Y7-11 schools. Relaxed uniform as in no ties or blazers, fabulous performing arts complex. Real feeling of purposeful activity. Feeds Peter Symonds, mainly with some DCs heading for Barton Peverell.
We chose this school as we needed one that worked for both DSs; DS1 is reasonably academic, so would have been fine at Kings or M'batten, DS2 is less clever, which is where he would have found himself in the 'C's at Kings and perhaps in classes with the less able and less well behaved at Mountbatten?
Avoid the northern Southampton schools (sorry!), and Toynbee, Crestwood and Quilley and try not to buy where you rely on the car park that is the M27 to get around.
South Wilts in Salisbury, 22 miles away from So'ton IS good but unless your DC is very clever or you've been tutoring, getting in is very hard. Salisbury is awash with Preps whose sole purpose is getting kids through the 11+.
Good luck!