I don't remember. Googling gave me these: http://educationnext.org/much-too-early/ http://educationnext.org/much-too-early/ https://www.education.com/magazine

I don't remember. Googling gave me these: http://educationnext.org/much-too-early/ http://educationnext.org/much-too-early/ https://www.education.com/magazine/article/higher-math-grades/ https://www.education.com/magazine/article/higher-math-grade... https://www.psychologytoday.com/blog/freedom-learn/201004/kids-learn-math-easily-when-they-control-their-own-learning https://www.psychologytoday.com/blog/freedom-learn/201004/ki...