My school seemed to know this stuff. But then again they really cared, b/c they wanted us all to take these tests by November. If not, you'd get an e-mail asking why. My school requires CK and CS passed to graduate.
I know people like to delay the CK, b/c they did well on Step 1. But if you time it right, you can have your cake and eat it too. I took my CK so that my scores came back after my school transcript went out. I choose to manually retransmit on myERAs, so I decided if my CK got release. I ended up doing better (don't know how, I studied during commercial breaks of my favorite shows), and retransmitted my scores. Guess what. Every program that I interviewed at was happy, b/c they knew that if they accept me, I could start July 1st, no problems. Same applies to CS.
My state requires you to be Step 3 eligible to start residency (means you need to pass Step 1, and Step 2 CK and CS). So either way, you need to take them and pass them. It'll make it easier for you to apply to residencies.