Hi Melanie!
I'm glad you're expressing interest in the BSW program! I switch into the BA/BSW program after my second year of sociology. Definitely read some of my course reviews to get an idea about what to expect:
http://www.macinsiders.com/forumdisplay.php/2nd-year-course-reviews-105p2.html?ltr=S&f=10 5&page=2
Yes, it is a very difficult program as you are being trained as a professional and need to understand the standards of social work practice. The profs are generally difficult markers so you really need to work to do well. There are a lot of great support systems in the school like McMaster University School of Social Work Student Association, Social Work Queer and Trans Group and the Disability Action Group, definitely get involved with everything in the program. It's a small program so you'll get to know the profs well and many will know you by name. We call our profs by first name, it's a really relaxed setting.
With regards to the SWAT, I graded several of them last year. I would say that you need to understand your social location (your race, gender, class, etc) and how that might impact the work you may encounter as a social worker. Also make sure you are up to date with current events, do some research about anti-oppressive practice if you haven't taken Social Work 1A06. You should also really research the profession and the McMaster approach to social work education.
http://www.ocswssw.org/en/about_sw.htm here is some info about the profession.
http://www.socialwork.mcmast er.ca/
Over the next little while start thinking about what the school's Philosophy means.
Hope that helps!