As a followup to lorelei and thumpers' comments, I agree.
If you stay within BU, you may be able to keep any academic or talent awards you already have. You MAY be able to even have them extended for the five year duration IF they were initially offered over your original four year program. You have to discuss this with with the department, financial aid office. At lot will depend on the school, their philosophy and funding, and your success within your current program.
If that's not possible, consider that if you transfer, you may have a significantly smaller aid package than you would get as an incoming freshman, although talent awards (including transfers) are pretty school specific. In general, state schools are more cost effective for a straight music ed program than private institutions, but the cost difference is sometimes offset by significant talent/academic awards from privates.
Another factor is your current status. Music ed programs are highly structured in terms of course sequencing. If you are currently a sophomore and could not switch to or add the music ed major until you are a junior, you might be better staying with undergrad performance and taking a masters in mus ed, rather than spending two additional years to finish a BMEd.
Again, your academic advisor, and department heads will give you the best options if you plan to continue the program at BU.
Here's one of my prior posts with a number of music ed thread links for additional info
Music Education Major trying out on Vocal --- Dilemma!! .