Also from experience, the King's turf is the nicest. Also is the only schoolboy ground (other than Barker which isn't remotely comparable) that has a proper 360 viewing. The hill is great to watch from too.
Personally I think the White Oval is the best schoolboy ground in NSW. Followed by Joeys. Also enjoyed Shore's grounds although atmosphere etc. isn't comparable (although Joker does highly recommend the pies).
King's turf is nice and green however despite it being quite green it is relatively short and actually quite a hard surface, especially with it being sand. Also, the cricket pitch in the middle may look green, however, if you walk out into the middle it is very hard underfoot (would be a pain to be landing on). To view the game, especially with it being a proper 'oval' it is quite hard viewing, especially from the far side.
Joeys has the best by far in terms of playing surface. Comfy and lush as well as great draining. As said Joey's seating is only good if you are a Joey's boy. Seating and viewing aren't the best otherwise.
View's surface is really good after a holiday period (as there isn't any traffic on it). Driving past yesterday, it looked quite lush and soft compared to usual. The cricket pitch can be a pain though later in the season. The best viewing is at View as you are on the hill and everyone can see the game. Great for opposing teams visiting as they are gifted with a grandstand.
Newington's actual playing surface is quite 'muddy' in regards to not much grass growth (put that to not getting the afternoon sun). Terrible if you're a schoolboy having to sit on the hill.
SHORE's grandstand is top tier, allowing both schools to sit right next to each other (potential for progressive banter) however the playing surface is not something to be fond of. You can see the dust curling up on a dry day and hear the thumping of boots due to how hard the ground is.
IF I COULD:
The best ground would be the SHORE grandstand (if placed closer to the ground) otherwise take Br Henry's grandstand, with View's hill and Joey's surface.