If you do Army ROTC, you do not have to do BCT at all.
If you want to do the Simultaneous Membership Program, then you do have the option of going to BCT, but it changed in about 2007 to where that requrement is no longer in effect.
Keep in mind that when you finish Army ROTC, you must still do Basic Officer Leaderhip Course II (BOLC) and BOLC III (formerly known as Officer Basic Course). However, these are nothing like BCT as you generally have evenings and weekends off and are not required to live in the barracks during BOLC III.