I would like to see the basics linear algebra taught in high-school. Lack of knowledge of linear algebra is extremely insidious. If someone who doesn't know calculus encounters a calculus problem, they recognize it as something they can't solve. If someone unfamiliar with linear algebra comes across a linear algebra problem, they see it as an extremely difficult algebra or trig problem. I've personally seen programmers apply trigonometry to problems that only require addition and subtraction to solve.