From what I gather.. their performance analysis showed that 10th graders taught algebra performed better than 9th graders taught algebra...

This is obviously not a reasonable metric due to many factors such as age, brain development, maturity and additional adjacent curriculum.

I don't get it though.. algebra is just variables right? Aren't we teaching programming to elementary schoolers? I know I'd written my first MMO bot by 9th grade...

Perhaps programming is a more 'tangible' way for children to experience algebra, rather than paper abstractions?