When I was a new teacher I would have croaked if I had had to write curriculum. And it would have failed miserably. What I did develop over time was the ability to extend curriculum in some realms. But I was glad to have a logical, tested curriculum for Grade 1 Reading. It's too important to be left to multiple teachers winging it.Right!
My ideal writing team, where curriculum is concerned, is a classroom teacher working with a disciplinary specialist. Classroom teachers have pedagogical content knowledge, mathematicians have the curse of knowledge, et voilà, at least potentially: real math kids can actually learn and comprehend.
(I'd always heard that the Singapore Math series was written by math teachers partnered with mathematicians, but Barry tells me that story is apocryphal.)
The only reason teachers can't write curriculum is that they already have a job teaching.
But these days, "our own curriculum" is often the teacher spending 5 or 10 minutes googling for a worksheet--this was our kids' 6th grade math from start to finish.Ditto.
Our school likes to say that the curriculum they buy (formerly EM, now moving over to SM) isn't their "curriculum," they just use that as the basic outline and go from there.
Now, there are some websites I love for worksheets ( http://freemathworksheets.net/ is my favorite,) and good sites for information and explanations ( http://www.purplemath.com/ for example), but nothing compares to a carefully constructed, brick-by-brick textbook for completeness, coherence, and consistency.
Here in these parts, the curriculum is becoming Google.