Best if you email and inform cic of ur proposed change; and if ur serious about changing colleges, irrespective of post secondary or post grad level of study, tell the IO then and there. I recently went through this few days ago and the IO called my new institute in front of me to confirm that I am registered and enrolled. Although she at first automatically printed my SP with the old college"s name (as I had got visa on that basis and hadnt informed cic about the change), my sP condition read "attend institute/college/UNi specified by immigration officer.) luckily I noticed this before exiting the area and ran right back to her, she then grilled me for not having informed cic before leaving India so they could have updated my file and college name and then hesitantly issued me new SP with new institutes name.
Although u can change legally by surpassing this condition even if sp is on old colleges basis, it's best to stay on the safe side and inform cic before hand and take SP of new college just what if they put a restriction.
The IO herself also told me they're cracking down severely on student permits cus of the volumes of students who leave college and start working illegally. So stay safe and be honest everyone!