I'm looking for rich educational resources similar to core-plus mathematics, for grades 7, 8, and 9. Is there any such material?
Core-Plus Mathematics is a product of NCTM standards, funded by National Science Foundation. Altogether, thirteen "reform" programs were developed, some for elementary, other for middle, and yet other for high school. They are "integrated" that is, thread algebra, geometry, statistics together with little success.
This curriculum has significant critics (see the Math Wars debates). Back to your question, Connected Mathematics is probably what you are looking for. But then again, Core-Plus is a high school curriculum and is supposed to start from 9th grade, so not sure where your 7-9 grades range comes from.