Hello Dls867.  My son graduated bot camp Aug 3, and went to Groton for BESS and A school.  BESS is "Basic Enlisted Submarine School."  It's about 6 weeks, and it's pretty much what it sounds like -- a basic introduction to submarines.  They have some quals to get through, some classroom time, some time in hands-on trainers (damage control, escape trainer, etc.).  They have a graduation ceremony upon completion, then begin their A school.  Depending on the A school, and whether they have a full class ready to go upon completion of BESS, they might start the Monday after BESS graduation, or they could have a small delay, waiting for enough students to form up a class.  My son started the Monday after the Friday BESS graduation.

Hope this is helpful!