An ROTC cadet/mid applying to an Academy has one avenue of Nomination not available to most applicants -- the Professor of Military/Naval Science. Inasmuch as Congressional Nominations are never guaranteed, this is an important option.
So... any ROTC cadet with aspirations of transferring into an Academy should not only make an effort to outperform every other first and second year cadet/mid, but also work with the PMS/PNS on a plan to secure their Nomination as well as written recommendation.
On the Academic side, the Academy will look for a first year college transcript that includes many of the classes mandatory for Academy cadets/mids. That would include English and Calculus, and possibly the first semester of Calculus-based Physics. Chemistry is also valued.