I remember my S struggling with algebra until, suddenly, the lights went on and he got it. It was the turning point for him in math; up until then, I helped him a lot with homework. After that, pretty much never, which is a good thing since I doubt I could remember calculus to save my life.
FWIW, my S really likes Khan Academy. I think it was his algebra teacher who turned him on to it. It’s online, it’s free, it covers a lot of subjects. It’s also not a bad skill for a student to have – to be able to “self-diagnose” their own weaknesses and figure out the way to address it.