In 1948, I learned to sew a straight line in Home Ec class on a piece of paper with lines on it to follow. We had to sew down one side stop at the corner, turn and sew to the next corner, etc. I had been sewing for years before that, but that was how the teachers taught the girls (only girls) to sew a straight line.
And by the way - boys do want to sew. You just have to give them a chance to see if they take to it or not.