Are you talking about high school or college? Because it's very, very rare for anyone to be a strong 5.5 in high school, unless he's a nationally ranked junior who plans to skip college to pursue a pro career.
I would disagree with this. Most 5.5s in high school would go on to play college tennis. A player that is 17 or 18 yrs old and isn't 6.0+ is not gonna make it on the tour.