Wu knows a good bit about the mathematics of fractions ... about as much as is known in the field of teacher-education. His article on CCSS-fractions suggest that he does not understand fractions as quantities (which is how the very young learn fractions).
From: Robert Hansen Sent: Sunday, October 28, 2012 11:41 PM To: Clyde Greeno @ MALEI Cc: email@example.com Subject: Re: The Teaching of Fractions
On Oct 29, 2012, at 12:36 AM, "Clyde Greeno @ MALEI" <firstname.lastname@example.org> wrote:
That mess came from his own efforts (as a traditionally educated mathematician) to function also as a mathematics-education consultant ... without thoroughly studying the mathematics of fractions.
I am pretty sure that Wu thoroughly understands the mathematics of fractions. (surely that isn't what you meant, was it?) I don't think Wu knows how to teach fractions to elementary students.