If there is a college seminary in your diocese, he can contact them to pursue eventual enrollment. If he is interested in a religious order, he should contact their vocations director for information. Unfortunately, there aren’t likely a whole lot of discernment programs for high school students, however; though there ought to be. In Chicago we still have a minor seminary (until June) and there will be a discernment group thing for boys come fall to at least keep something out there on the table. But this is not the norm nowadays. Sadly, most boys that age will basically be told to get back in touch in a few years, as nobody wants to bother investing in their development, if they even believe in the ability of someone who is of that age to actually be called or respond.
More essentially, though, have him find a priest whom he is comfortable with and ask that priest to help guide him along the right way.
