A major reason that your school sends 30% to Ivies is that at least 30% are legacies for Ivies, there are a good number of kids of donors who attend your high school, and your school also likely has sports which are not common outside of “elite” boarding schools, but for which Ivies recruit.
If you do not belong to one of these groups, you will likely need to be in the top 10% of your class to be competitive for colleges with acceptance rates of below 10%. Also, your high school counselors may not have the same type of connection with WUSTL and CMC that they have with “elite” East Coast colleges.
I would disagree, though with @tsbna44, and say that Tufts may be a possibility, depending on what your counsler says, but Macalaster may not, since they may not be as familiar with your high school. However, colleges like Lafayette, Skidmore, Trinity (CT), Bucknell, etc, could be possibilities.
I will also disagree somewhat with @Publisher and @aquapt and say that you may want to choose an East Coast reach, because of the connections that your school likely has with many of the NE colleges.
However, again, you need to speak with your Counselor, and ask them what they think. They likely know which colleges are your best bets.