Sugar-coating teaching

In elementary school, they teach you that to subtract, THE BIGGER NUMBER ALWAYS COMES FIRST.  They teach you to CELEBRATE CHRISTOPHER COLUMBUS BECAUSE HE IS OH SO GREAT.  When I went to middle school, I was getting all confused because of this thing called negative numbers. Um, teacher you must be confused because negatives aren't a thing. Come high school, and I'm finally learning about Christopher Columbus's true colors, which completely changed my prospective on the while discovering America. Why do teachers give false information?