Berlin is such an interesting place and with so much to see. You really shouldn't talk yourself into apprehending the trip as something bad Shenji.
I was there (also on a class trip) in 2003 and it was one of those weeks where you had sore feet every evening but it was really worth it!
Berlin for example houses the largest complete dinosaur skeleton (Brachiosaurus) in the whole world. There is so much to see about the history of the town (Berlin Wall, Checkpoint Charlie and all that), the Regierungsviertel (governmental district) is also quite a sight (but you have to wait for a long time in queue if you mean to enter the Reichstag building). There is the KDW (one of Germany's largest shopping centers), the Televion tower (highest building in Germany I think), there is Schloss Charlottenburg and also within range there is Sanssouci. There is the national gallery, the Museumsinsel, uncountable interesting places... oh gosh I would really change with you if you don't like that prospect
