Check out this great Post By Ryan Woodruff.
There is a belief common to many swimmers and their parents that one's junior year of high school is the "make-or-break year." They view the junior year as a swimmer's final opportunity to earn a spot on a college team. I won't argue that the junior year isn't important, but here are a few concerns I have with emphatically taking this approach:
http://www.theathletevillage.com/blogs/ryan-woodruff/2010/03/19/junior-year-myth