Super Alice:Yes. The web site claim that. My DS is in non mandatory uniform group. However, DS came back yesterday and claim that the HOD in charge of CCA say that Sec 2 cannot change CCA and only Sec 3 then can change. Not sure how true. I think at Sec 2 level still can change. Because, they are not sure what they need at beginning Sec 1. I would say that it is more of the trial and error stage. After 1 yr of Sec experience, it seem like they know what they need. if wait till Sec3 then change, it serve no purpose as they are suppose to prepare for 'O' level.
If HOD mentioned cannot change, then you have to bring this up to the principal. Try to provide more info why your DS wanted to change CCA.