@ReminiscingDad Although I agree with you about most schools’ inability to teach Math, I believe that parents are #1 ultimately responsible for their children’s education. We need to pay attention to our children’s education and address any need right away. In the case of Math, because its sequential nature, little gaps in 2nd grade, if not taken care of, are bound to become craters later on.
We went through something like that with our second child, our daughter. At the end of 2nd grade, she tested in the ~50% in Math. I remember thinking, oh lord, poor thing she got my genes 
I was already assuming that she would be “not good at Math,” just like me, who, coincidentally enough, started having Math problems in 2nd grade. In other words, I was waiving the “white flag” on her
Papa was not having any of that. He would take care of it over the summer. He bought Math workbooks from Barnes and Noble and practiced with her throughout the summer. At the end of that summer, the little girl was as sharp as a butcher’s knife! Official state testing here in FL starts in 3rd grade, my daughter got a perfect score in Math that year and has continued doing so ever since. A summer focused on her Math completely changed her academic trajectory. Since then, she has excelled in Math and wins the top Math award at her school every year. She is currently in 7th grade, taking Algebra 1, alongside 8th graders, and is the top student in the class. Her teacher brings it up all the time to tease the 8th graders 
I compare my daughter’s story with my own story and realize that if my parents had paid attention to my Math in 2nd grade, I wouldn’t have struggled as much with Math throughout my life A parent does not need to hold a PhD in Math to help a child with 2nd grade Math.
I think that the key is parents having a positive attitude towards Math. I’ve heard too many parents talking about how much they hate Math/trashing Math in front of their children. I’m sorry, that is not a positive message. As a rule in our house, we never, ever trash any subject. We let the kids know that every single subject they take at school makes them an educated person, therefore, every single one is important and deserves their attention.