How many boys after 8 in coed preps in London?

[Mummms]

Have been looking at some prep schools in London that are coed but it seems like the number of boys after year 3 and 4 start to drop off and boys move to the bigger single sex schools instead of staying all the way up to 11.
Has anybody experienced this where is caused problems if their son stayed on when most boys left?
Do only boys struggling stay on that didn’t get places at other schools?

Depends where you're looking. I know the ones around Dulwich stay fairly even because the boys going there are balanced against the girls going to JAGS.

We’re slightly more central than Dulwich, more around the Kensington & Chelsea, Fulham area. I’ve noticed it seems like boys leave in schools such as Garden House, Norland Place, Cameron House. Obviously lots of single sex schools in the area though, but I’m assuming most boys that are leaving these schools are moving to others such as Westminister, Dulwich College, Kings, St.Paul’s, and even Wetherby Prep or boarding preps. The only coed preps that doesn’t seem to have an issue with this are the Thomas’s schools (or others that go up to 13, so maybe that’s the main reason for it…)

As you've said, I think it’s because those schools only go through age 11 and many of the families are thinking about boarding for their boys for senior school - and most of those start at 13. So they move either to a through school (which might have boarding too) or to another prep that goes to age 13. Even if not considering boarding, they can avoid the 11+ nightmare by moving earlier.