I agree with the recs you’ve already been given about U. of Rochester, Case Western, RPI, Colorado School of Mines, Vassar (as a hard target for a male like your son), Occidental, WPI, and Brandeis.
A few target schools that your son may want to consider that I haven’t seen mentioned yet include:
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College of William & Mary (VA): About 6800 undergrads and might be a target for a male
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Oberlin (OH): About 3k undergrads
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St. Olaf (MN): About 3k undergrads
And you said you already had safeties covered, but I’m just going to put a plug in for Gustavus Adolphus (MN, about 2100 undergrads) and Lawrence (WI, about 1400 undergrads).