Learning environment matters, but I wouldn't say that it would completely change the outcome. If you are smart you don't have to work hard or have a good environment to understand high school maths. If you aren't that smart you can still pass the courses with hard work, but from my experience teaching a lot of college students in 1:1 settings people who have to work hard never really grasp the subjects. And some are so lacking that even with hard work they still can't pass.

So basically, just because someone managed to improve their grades and pass classes with hard work doesn't really say anything about my points. There are still people who pass easily without any of that. In short, my view is that hard work and environment can help improve your results, but unless you are completely prohibited from attending school you wont need that if you are smart enough.

For example, I skipped a lot of classes, was abused, was suicidal, never studied for any tests and didn't do any homework assignments in high school. I still got perfect math grades. Most people have better environments than that and spend more time on maths than that yet still do worse. I spent a lot of time doing 1:1 teaching in college, explaining things in intuitive ways etc helps, but ultimately I had to conclude that I can't make others understand things the way I do. They simply lacked something.