There have been several replies by women of the opinion that it's OK for women/girls to bathe young boys. Through my experience, I have a different opinion.
As a 12 year old boy, my older sister, younger brother and I spent a summer at my aunt's farm. She had 4 boys; my twin cousins Kenny and Karl were my age and 2 younger boys. My aunt informed us that she had neither the time nor hot water for individual baths and that every night she showered her 4 boys locker room style with a garden
hose. My brother and I would be showered with them. I was rather unsure what all this meant. I was led into a utility room with everyone. I was extremely uncomfortable as I had to strip naked with the other boys in front of my aunt, who then proceeded to spray us with water, gave us soap and shampoo, instructed us to wash our hair, etc. Even my mom hadn't seen me naked for probably 2-3 years at that point.
After a couple of nights, she told us that my sister Donna would assist her by helping with the two youngest boys. It was extremely embarrassing for me (and the other older boys) to take our clothes off and be naked in front of my sister. None of us boys had any pubic hair yet. We all had erections at various times throughout these showers. As a 12 year old boy, it was totally humiliating to have my erect penis pointing straight at my older sister.
There seems to be a philosophy among many women that pre-pubescent boys are not allowed any privacy.