If you have standard children, then the California Content Standards will do. But I’ve never had any parent admit that they had a standard, average child.
Some children are fairly bright, and able to learn all sorts of stuff quickly.
Other children have a learning disability ad need to take it slower and with fewer topics.
Sometimes an “easy” book is just right for the bright kid trying to learn a new subject.
Sometimes a “slow” child in many topics is an absolute genius in a specific topic and can read at a high level in that one topic.
Any thing that someone else says your child “must comprehend” in a given year is not concerned about YOUR child!
The standards are written for curriculum publishers so that they’ll be sure to cover all they need to over several years of text books. This way a child won’t have to have a lesson about, say, Roman Numerals, even year ad nausium.
Homeschooling you can present new concepts as your children express curiosity about something. They will then probably learn the concept in about an hour because of high motivation.
Force feeding them concepts because they “should” learn something at their age will take hours to teach and then minutes to forget.