01/31/2018 01:33:22 PMWe all have those pivotal career moments. For Elliott Witney, it happened in his first year teaching two decades ago. Three months in, he asked his fifth-graders whether a math lesson made sense. A student named Brenda responded: “Yes, Mr. Witney, we learned this before. Our teacher taught us this last year. He taught us everything you taught us last year.”