I'm on my phone, so must be brief. They use EM in my district. IMHO it is unsuitable for use with a HG+ math student as implemented in our district. It is a heavily spiral curriculum and characterized by endless constructivist drills where children "learn" to construct number relationships in different ways, etc. For someone with math talent a lot of this is just so much fluff.
Even knowing the history, pedigree and intent of EM, it would never be my first choice for any student. For an advanced student it presents a real danger, as it is chock full of opportunities and encouragement for teachers to insist that the student go "wider instead of deeper", but in meaningless, wasteful ways.
My son utterly hates it.
