Well, if you make it clear to the IO when you come back that you were STUDYING (take proof just in case), chances are you'll be allowed back in oke. If you want to be REALLY on the safe side, get an expedited Re-Entry Permit BEFORE you go. This means, apply for it and do the biometrics before you go, and hopefully they'll send it to you soon after (ASK FOR IT TO BE EXPEDITED). As for the continuous residency, you can TRY to come back in the middle of your studies for about a month, but this is no guarantee that, when you apply for citizenship assuming NO break in continuous residency, the IO handling your case will agree with your assumption. But, that's about all you can do, I think.