One example of how to implement this is to reduce or eliminate accelerating mathematics in the middle school. Spend time there on problem solving and going deeply instead of teaching multiple courses in one year just to get to Calculus faster.
I'm so tired of how much time we spend teaching math that few will ever use during their entire life, just in case a small percentage of us might need it.
Like I've used almost nothing I learned in Geo, Alg 2, PreCalc, and Calc but I need statistics and other math all the time.