I have DCs there, and they are truly loving it. The (not so) new Head has made changes, but only for the better, IMO. She genuinely has the children's best interests at heart, both academically and pastorally, and in the process of recruitment has recruited staff accordingly, resulting in a great mix of passionate teachers, some longstanding with many years experience, some brand new to teaching. There are a lot of male teachers for a small co-ed prep school, which I think is extremely refreshing and says a lot for the environment in which they find themselves. The male teachers often coach the girls sports teams (each competitive team has its own 'head' coach so to speak, so they get to know them very well) with fantastic results - rarely do I see male sports coaches on the girls sports fields of other schools when I travel to Away matches but I think its a positive experience for the girls that they can have male input in a female sports environment.
Re: prep for the next stage of education, our experiences of the support at this stage has been nothing but good. Its true the school finishes at year 6 and there is no direct link to a senior school, but I see that from a positive angle. Because it is truly independent of any other school, we have had practical, honest advice and support on which senior schools would suit our DC. The Head and the (extremely dedicated) Deputy Head(and Department Heads come to that) are very well acquainted with the Senior Schools that the children generally apply for; if your child is applying for one they don't know one, they will make it their business to get to know it, in order to support the family. The kids are extremely well prepped IMO; my DC came home over the summer hols prior to year 6 (and again over Xmas) with a bespoke study pack covering the types of paper at the schools they are applying for. They also provided 2 (optional) week long refresher courses (one each of Maths and English) prior to beginning in Year 6, so that the kids could hit the ground running. There has been no bias or 'pushing' us towards any particular school for 'good publicity' (for example, for bragging rights that they have had X children accepted into X amazing school) or other reasons and no pressure to apply to one over another. The Head and Deputy have been great in their support.
I do understand (but haven't experience of) the practicalities of having children, esp. boys, leaving at 11, when a lot of the suitable senior schools start at 13, but friends whose sons in particular have been through it, have no had any problems as far as I know with their children attending a different school for the two extra years. Some of them have said their child enjoyed being at the 'top' of a school for another two years and got a lot out of it, confidence-wise. One said it also meant they had the opportunity to revisit the choice they made for their pre-pubescent child's, who was now a very different person!
Kids also sometimes go into the State system at 11 too from Longacre and the school does do SATS as well as the usual prep for 11+.
Academically, the school has definitely upped the ante in the years since the incumbent Head took over - children do regularly get accepted into the 'best' academic schools, often with scholarships. However, they don't always take up the places in the end, so it may seem that the school doesn't really feed the academic schools, which is not true. Equally, many very able children don't even apply for those schools in the first place, even though they would in all likelihood be accepted into them; families simply sometimes choose not to put their kids into those more academically focussed environments for whatever reasons, it's maybe why they chose Longacre in the first place?
Pastorally it is great - the House system is successful throughout the school, with even the Nursery children and all staff being in Houses. They hold regular House competitions, the most recent being a dance one - everyone in the House from the 2 and a 1/2 year olds to the teachers took part! - and the older children regularly help out with the younger ones, through prefect duties and so on.
Lower down the school, Year 3 upwards in particular in response to the first question, the school has also been supportive. the transition from pre-prep to prep has been smooth and my DCs have always been very happy. Lots of kids join in Year 3, often from state infant schools, so your child wouldn't be the only 'Newbie' by any means! The Early Years and Lower School is simply lovely.
I don't think the children / school body goes on show for Open Days, though I know mine love them - I think its a chance to show off about their school! I do know for sure though that when the kids show prospective families around, they are not prepped at all, in what to say / show - it has been known for families to see the toilets, broom cupboards warts and all, courtesy of my children, which shows the school is confident that the children will paint a happy picture, I think.
There's a great building project going on too of course, which is going to provide brilliant facilities in the future.
(I don't work for the school BTW, in case you were wondering, but I do have happy kids, hence the feedback...! Good luck in deciding..!)