Mae Ysgol Gyfun Cwm Rhymni yn pwysleisio pwysigrwydd ymddygiad da, priodol ac agwedd barchus. Ceisiwn hybu hunanddisgyblaeth ymmhob agwedd o fywyd yr ysgol drwy feithrin parch at eu hunain, at eraill, ac at safonau moesol, academaidd a chymdeithasol mewn gwersi, ar y cae chwarae, ac mewn agweddau eraill o fywyd ysgol. Anogir y disgyblion i weithio, dysgu a thyfu gyda’i gilydd mewn awyrgylch addysgiadol gyfforddus. Er bod canllawiau ymddygiad ar gael yn ysgrifenedig (Polisi Ymddygiad) credwn fod dysgu drwy esiampl yn fwy effeithiol. Pan fo angen cosbi, ceisiwn ddod o hyd i gosb bwrpasol ac adeiladol.

Ysgol Gyfun Cwm Rhymni emphasises the importance of good, appropriate behaviour and a respectful attitude. The school strives to foster self-discipline in all aspects of school life by nurturing respect for oneself, for others and for academic, moral and social standards, in lessons, on the games field and in other activities. Whilst there is a written code of conduct, we believe that learning by example can be more effective. When the need for punishment does arise, we look for an appropriate and constructive form of punishment.