Ed school mole John Dewey has posted another letter at Edspresso. This time he clarifies the definitional problems with constructivism. Mr. Person (of Text Savvy) and I discussed this very issue here.
My view is that it's not constructivism when you've given the student all the information to solve the problem. And, almost every teacher provides some kind of guidance and scaffolding during instruction because unguided discovery learning doesn't work.
It really doesn't matter what you call it anyway. The only thing that matters is what the students have learned or haven't learned at the end of the day and what they've retained by the end of the course. In math, it's easy to determine what works and what doesn't: how well the student solves math problems he's been taught.