It shouldn’t be a big problem. Remember what our kids do in high school is the same materials, and at a higher level, than what the goyim’s universities do in graduate school (e.g. classical materials in original language, with medieval texts in the original). If he’s a good learner, it means he can prepare on his own as needed for whatever subject he’s interested in, even a hard major such as ones requiring serious math such as the sciences, engineering or economics. All it takes is brains and hard work, and if he did well learning Torah, college will be piece of cake.
Of course “easy” schools like Touro are fine if you are rich, but if he’s smart he probably can get a scholarship for a much better school. And of course, there is always the option of distance education or a public university.