A “rigorous curriculum that is easy to implement” is oxymoronic. Reading, answering comprehension questions, memorizing highlighted vocabulary words, and having the grading rubric predetermined by the publishers does not make for a rigorous education. It is simply learning to identify what to regurgitate the points someone else has determined are important.
A rigorous education is thinking for yourself about what you’ve read, analyzing, finding what points resonate with you, then persuading others to see the work as you do through persuasive and logically constructed arguments. It is taking what you’ve read and learned then applying it in unique situations. Of course it is harder on the mom -- it is harder for the student, too and that is the point. It is far harder to think for yourself and defend your thoughts, but that is ultimately more important than being able to parrot what you’ve read.
Grade levels, reading levels, lexile numbers -- all those are handy measurements when dealing with a school full of children. In your home all that matters is the child in front of you. Meet each child at his or her level then move forward. Read, explore, talk, create and have fun. And talk some more, encouraging your child to express opinions and all his or her creative ideas. That is when the real learning happens. Spend some time each day on skills but don’t make it the sum total of your existence. The skills are simply tools for furthering the joyous endeavor of learning.