I remember when I 'got' algebra. I was in 10th grade in Chem class. We were using mols = (mols/Volume)*Volume. For weeks, I had no idea what was going on. I just plain did not understand algebra whatsoever. But finally, at the end of a lab class where we actually mixed things and then found the concentrations and volumes, I finally figured out that these algebraic equations actually tied back into the real world. This was not for lack of trying on my part, my teacher's part, or the schools. I just plain did not understand. I think it was a developmental issue for me. I wasn't ready to chemo-mentally, therefore I just muddeled along frustrating everyone including myself.
I say this because I went on to get a BS in physics from a UC. Obviously I learned math very well later on. But in 9th grade, I was unable to learn anything harder than long division. I was a 'left-behind' child due to my brain. Nothing, I believe, could have helped me. Not all the tutoring in the world. My brain wasn't old enough then.