Sure, an NFL safety MIGHT hit 235-240. Who was the last college safety to do so? Sean Taylor was barely 230 and he was considered very big.
A lot of kids stop growing before HS finishes, but they've still got a lot of room to add muscle mass. My buddy was 5-10 or so and started out just under 180. In less than a year in the
OSU S&C program, he was a rock-hard 195-200. Besides the OL, I would question anybody that didn't put on a good 10+ lbs. of muscle in one year under that program. It's very intense.