Also, sailing schools WANT you to pass. They dont make money or get a good reputation by failing students. If you arent getting it they will go over whatever you didnt get so you can pass.
I asked the instructor in one of my ASA courses if he had ever failed someone. He said yes, there was a guy who just couldnt concentrate enough not to pull dangerous stunts like sudden turns or mistaking port and starboard and he felt it would be wrong to pass him since he might endanger people. He also said that the point he thought a relatively high bar should be imposed is the ASA 104 exam which certifies you to go off and captain a bareboat. Even then he said the goal was to help people pass if they could reasonably do it in good conscience. He also said almost all of the people willing to cough up hundreds of dollars for sailing lessons really did want to learn all they could so he rarely had a problem. Basically, he said (as people above did) that most folks had the desire so they did fine.