Not always. Depends on the person and their body types/metabolism.
I know kids who couldn't gain a pound in HS, eating everything in site....but then were able to do so in college as they matured. I know other people who couldn't gain weight until their mid 20s, and that was going to the gym every day and eating plenty. One was a bodybuilder with a ridiculously rigid diet in terms of calories and timing...and no matter how hard he pressed in bulking phases, he was barely able to put on size until his body matured in his mid-20's to 30's. Even with nutritionists on staff, they are not with these kids 24x7 and unless the kid is dedicated to his craft, it could be difficult if he's naturally skinny.