Not a regular here, and not female either. I went to Shiplake, as did my cousin. I am also still very much involved in rowing. It depends on your child's academic needs as to which school you choose - they are, after all, very different and all have a different ethos. Happy to advise.
On Shiplake, it is certainly not a school for thickos and I take exception to that. They have a very inclusive policy and their real strength is in getting the best out of everyone. Whether your thing is sport or academia, most boys thrive there. Boys go on to all the major universities as well as into spoting life. Witness Ben Hunt Davies who now has an olympic Gold medal to his name (albeit he was there in my era and left in 1990). They also award rowing scholarships.
There are many schools who row and not many who are actually very good at it. Look over the past couple of years at the National Schools' Regatta results (a better indicator than Henley which is stuffed with Australian and USA crews). Many are not boarding schools.
Those boarding schools who I would deem 'consistently' good at rowing are: (in no particular order)
Abingdon
Radley
Shrewsbury
Eton
Shiplake
St. Edward's
Bedford Modern
King's Chester
Other schools may chuck out the odd freak crew, but these are the ones who are always up there (the list is, of course, much longer if you include day schools)