good question 回复：为什么学习的进度不能以为标准？

some people assume that 美国小孩 do not learn too much, but they learn by doing (through hands-on method) and they can apply to real life and they may turn out to be better problem solvers.

it's a good idea to allow children to make mistakes and learn from mistakes, even though it may take longer time. see Diana Laufenberg on learning from  mistakes: http://www.ted.com/talks/diana_laufenberg_3_ways_to_teach.html