I seem to have a problem keeping white school shirts and white socks looking clean and white. I use a non-bio washing powder due to sensitive skin so I'm not sure if this perhaps is part of the problem, maybe the washing powder isn't powerful enough to lift the dirt properly. My daughter's white socks look dirty and no matter how hot I set the water to they just won't come clean. They smell fresh but look stained. White school shirts after about six months start looking dull and off-white. I do sort the washing so that whites are only washed together and not mixed with darker colours. Should I try doing a pre-soak with another type of soap before putting it through the usual wash? Other children seem to have pristine looking white shirts, is there a knack to keeping them white or are parents buying new every few months?