Your got to understand that it is their life,
not yours :) I told my kids that they actually save me money if they do not want to go to college. Just FYI, they are straight A students and I keep telling them it is ok to get a BCD or F! They have to learn from their "failures".
I also told them that they should not count on me providing financial support for their college if they do chose to go. They should plan for getting scholarship or student loans. My job is to make them as good a person as possible until they graduate from high school.