One of the beauties of homeschooling is that kids can work at their own pace based on skill mastery rather than age or grade level. This is helpful for all subjects but especially ones with physical coordination aspects like handwriting. Kids are all over the map when it comes to physical development.
Is your kindergartener’s printing better than your spouse’s? No need to hold them back with a “kindergarten” book! Does your older student need extra printing practice before tackling cursive? No worries! You can use whatever resources meet him where he’s at based on ability, not necessarily grade.
At the end of the day, the goal is to have kids who can write neatly (or at least legibly) to communicate in written form.