Is it possible to upgrade from the cs5 design premium student edition to a normal cs6 design standard version?
Or do I have to buy a full version of cs6?
You can upgrade from DP CS5 S&T to DS CS6 wihtout any issues.
Check the below link for the upgrade pricing and other details.
Yes, but you'll be better off going to CS5.5 now. If you do the cost will be much lower since you'll get a free upgrade to CS6 when it ships.
CS5 to CS5.5 Design Premium is $399 with free CS6 Design and Web Premium.
CS5 to CS6 D&WP is $750.