Jo Boaler, professor of Mathematics Education at Stanford University has published two important pieces in the Hechinger Report that I encourage you to read.
One article is titled, “Memorizers Are The Lowest Achievers and Other Common Core Math Surprises"
And the other is, “Should we stop making kids memorize times tables?”
Jo Boaler is the co-founder of http://www.youcubed.org and author of What’s Math Got To Do With It: How Teachers and Parents can Transform Mathematics Learning and Inspire Success. (Penguin, 2015)She also offers a wonderful online course for parents on How Students Learn Math through Stanford University's continuing education program.