Sorry no-one has answered you. I've name changed for this but wanted to help.
Large doesn't necessarily mean bad. Depends on your child and the friends they find.
Reigate Priory is large yes, but they manage it well. Teaching style works well for many - immersive and engaging, some based outside in the park. It's an exciting school to be a part of and they really make it a big deal for the children to be part of it. Wonderful old building but the school may move in 3 years' time to the south side of Reigate - this is currently being considered.
Reigate Parish - IMO works very well as an infant school but still needs some time to adjust to being a junior school. Amazing (new) building for the juniors, but anecdotally weak leadership, and by all accounts riven with cronyism and favouritism - bit of an intense middle class mummy environment which filters down to the kids. That said the school has lots of fans - who tend to be more vocal than those who have had bad experiences. But you'll find a fair few of the latter if you ask around.
Parish doesn't have an official intake at Y3 but if you're looking at in-year admissions for primary schools as well as junior then I'd also recommend looking at schools like Wray Common and St Joseph's. Both two-form entry so just as small.
Definitely worth looking at St Josephs if you're a churchgoer. Nurturing, faith-based, fair and strong educational standards. Feedback overwhelmingly positive - I've not heard a bad word about it. I'd choose St Joe's over the Parish every day.
Someone on here once described Wray Common as chavvy - I'd disagree. I have friends with children there and it's certain;y not a word that comes to mind. Strong leadership, teaching pretty similar to both other schools, lots of outdoor space - and its own swimming pool (save $$$ on weekly swimming lessons). Bit of a hidden gem.
St Bedes is a big school but with that comes lots of opportunities to make friends, greater choice in clubs and GCSE / A level options. I think it used to have a really good head but he has just recently retired and I don't know much about the new one. The results probably speak for themselves - I know lots of parents with children there - most happy. Seems partly down to the luck of the draw with respect to cohort.
Might be worth looking also at other state options for secondary too, depending on where you live, such as Reigate School (also big but smaller than St Bedes because no sixth form - a bit like marmite, some love it, some consider it to be a bit chavvy too) and RAA. My two are at the Ashcombe and I would wholeheartedly recommend it, but it's Dorking, so depends on whether you're happy for your DC to get the train.
Hope that helps.