Four of my students have already been invited to SLE so notifications are on-going through April (as noted previously). By the way, all students should be preparing for the CFA; however, if they are headed to SLE then they will have an 'early' opportunity to record a good score there during the program. The same is true for NASS and AFASS.
If your student is not invited to SLE, there are other great ways to see the Academy. One good route is by attending one of the USMA summer sports camps. Many of my students have participated in them across all of the SAs. Students stay in the dorms, eat in the mess hall, meet cadets and staff, and they also work with the coaching staff. Good luck!