Too often elementary school teachers teach incorrect "mathematics" and also communicate to their students that mathematics is too difficult for ordinary mortals. "If my teachers doesn't understand this, I can't either." Such intellectual and emotional damage is so devastating that even a teacher who is mathematically competent will find it very difficult to undo.

(From "Is elementary education a concern of MAA members?" by Patricia Clark Kenschaft, MAA FOCUS, August/September 2009.)

Another article by the same author (2005):

Racial Equity Requires Teaching Elementary School Teachers More Mathematics.