Parents around CC will say, a safety is a school that: (1) a student is almost certain to get into; (2) is affordable; and (3) the student will be happy to attend. That third one is often the sticking point for high-achieving kids, as they often envisioned themselves somewhere prestigious. But for a student who is serious about pre-med, minimizing debt, especially with generous merit awards, is an important part of the strategy.
You can look at the Common Data Set (google, for each school of interest), to see where the distribution of test scores and gpas fall. A student who falls within the top 25% of scores/gpa where acceptance rate is (people disagree here about where the line is) is something above 40-50% (my somewhat arbitrary figure), a student probably looks solid but not a lock for admission. An easy error to make is to look at stats for schools with below 20% acceptance rates, see that a student is in the top 25%, and figure they have a good shot at admission. Most of those schools are just not predictable enough, and certainly not when you hit the “lottery” schools with below 10% acceptance rate. Those schools are rejecting students who are every bit as qualified on paper as the ones who are admitted.
The typical advice for pre-med is to minimize undergrad debt at all costs – since a student will presumably have to borrow it all for med school. As med school admission is largely a factor of gpa and test scores, plus having engaged in shadowing, research etc., there is not necessarily a strong advantage to to pre-med at Northwestern over, for instance, Pitt. We know a number of kids who took generous merit at “lesser” schools and are now in very competitive med schools.
Since your student is comfortable with the 15,000 range, you might keep UW as what should be a safety (as long as his essays are solid). UW shrinks pretty quickly once students sort into their respective Colleges. The opportunities for undergrad research program – by application – for freshman, as well as the Honors program, can be quite impressive for a UW undergrad. I’m biased, of course, my own student is at UW (OOS), and has had a phenomenal education, with world-renowned profs, close relationships with his professors, and competitive internships. Of course, UW does not give a lot of merit, but as your instate flagship, it offers a good instate rate and not excessive room and board costs.