<p>I would recommend you start off at McCormick and apply to MMSS as a sophomore. According to the website, for sophomore admissions, they give preference to applicants that completed and performed well in a freshman honors math sequence. If you do really well in first-year math at McCormick, you would be a really appealing candidate.
And getting into McCormick is better than not getting into Northwestern at all. You could just transfer as a sophomore.
Here’s a link to the page I was looking at if you haven’t already seen it:
[Sophomore</a> Admission, Mathematical Methods in the Social Sciences – [page headline], Mathematical Methods in the Social Sciences – Weinberg College of Arts and Sciences, Northwestern University](<a href=“http://www.mmss.northwestern.edu/admission/sophomore.html]Sophomore”>http://www.mmss.northwestern.edu/admission/sophomore.html)</p>