I would say start them out after they learn their colors. I think a good age would be around seven or a little after. They can begin by knowing the difference of why sorting their whites from the deep dark and other colors are important. When the adult feel confident that they know how to operate the washing machine and dryer properly, how to measure the detergent, how many clothes to put in the machine at one time and when to put into the dryer, then it’s time.
That’s a good answer. My 7 years old helps me with the laundry . He even asks if he can switch them over for me when the washer is done.