"Here’s your friendly reminder that grade levels are an artificial construct. They didn’t exist until 100 years ago. They were designed specifically for mass education in public schools.
It doesn’t matter what grade level of math or grammar or science your kid is in. What matters is that they are always progressing. Checking off boxes like grade levels is a trap full of stress and guilt, yet for some reason, homeschoolers insist on copying the very system they claim to disdain.
When people ask me “what do you recommend for 3rd grade grammar” or “6th grade science” I don’t give them the answer they’re looking for. I don’t know what 3rd grade grammar even is. I just know that my kids start with phonics, then reading, and then learning to spell based on phonics rules, then move on to copy work, and by about middle school they take their first Easy Grammar course. It’s the same with all subjects.
Progression is the goal. Being well-educated is the goal. Not checking off a list. So if my kids take pre-Algebra at age 10 or age 16, it’s not a big deal. What’s important is that they grasp the content and are able to move on to the next level.
It’s like video games. Just keep going until you level up, and if the kids aren’t getting it, stay in that world a little longer. If they are, advance to the next level. 
Have confidence in your ability to make decisions for your kids! A curriculum is only a tool; YOU are the one in charge of construction." -Nicky Truesdell
