Math Frustrations

I knew things wouldn't be smooth sailing all the time, but I came to a realization today. Laura had been struggling with Math since we started homeschooling. I know it's only been a week, but I couldn't figure out why she was struggling so much. In school, she was honor roll. As I was teaching her we kept running into concepts about which she had no clue. That bothered me because this is early in the book. She was getting frustrated and so was I.
Then I talked to a friend. She gave me a website to have a free assessment done. I hadn't done that earlier. I didn't see the point when my daughter had been honor roll. Silly me. The assessment showed her at a 2nd grade level...not 3rd. WHAT??!
I got online and began to look up standards. Why are Indiana Standards behind the standards of pretty much every major Homeschool Curriculum Math Textbook by about a year? Maybe it catches up at some point, but right now I have to find a second grade math book for my daughter.
I explained to her that we would have to go back a little and slow things down, and that she would be using a book that said 2nd grade on it, but if she was in school it would be third grade. I think she understands. At least, I hope so because I don't want her to feel that she failed in some way. This is not a reflection of her ability, just a reflection of what she has been taught to this point.
Maybe now Math won't be so frustrating for her. I am relieved now to know that I am not inept as a teacher. I am also relieved that this situation isn't something I could have prevented. Laura was taught at a lower level, which is the standard for either this school district or the State of Indiana...probably both.
It's only been a week, but I am beginning to see why Homeschool students often surpass Public School students.