1800 is a natural target next, which moves him/her to the top class: Class A. At that level, s/he will be considered as a strong player in most standards. S/he should be on almost all Top 100 lists of his/her age. S/he should also win some state and national champions here and there.
As a top scholastic chess player, s/he will play more large national tournaments and international tournaments.
After reaching that level, s/he definitely needs a GM or IM to help him/her further develop his/her chess career.