Latin spoken at public schools

Here “public school” has its British meaning (Eton, Harrow, Rugby School, etc): see http://en.wikipedia.org/wiki/Public_school_(UK).

I have heard occasional old accounts of pupils at the big fee-paying schools called public schools, being ordered to use only Latin, not English, for general conversation among each other, all the time, or on some days, or suchlike. Is this an urban legend, or true? When and where did it happen?

Best book I have read on that fascinating subject, which does indeed contain accounts of Latin use in schools:
Latin: Or, The Empire of the Sign
Françoise Waquet
http://www.amazon.com/Latin-Empire-Sign-Françoise-Waquet/dp/1859844022

The book looks fascinating. An extensive preview is available on Google Books:
http://books.google.ca/books?id=jgeV5UEKWggC&printsec=frontcover#v=onepage&q&f=false

I now have this book. It is useful.