Hello-
It really depends on the school. However, you will definitely be required to dress in professional attire when you work in the clinic no matter where you are. You will be sent home to change if you are not appropriately dressed to see patients.
For UCBSO, you can wear casual clothes (i.e. jeans) to lectures and labs.
When I interviewed at SCCO last year, the administrators told me that professional attire was required everyday in lectures. The students I spoke to said that was only enforced the first week of class. The SCCO students also told me that only a specific "SCCO thermal mug" purchased at the bookstore for ~$20 was allowed in lecture halls. I'm sure that's not really enforced. =)
Best wishes,
Rosanna