Really? My decision not to prewash is based on my personal experience and knowledge not a lack of organizational skills. I'm taking a knitting class and my bag of supplies has been packed and ready to go for 2 week.
People that show up unprepared should be expected to catch up or rebook. Prepared students should not be punished for others mistakes. while I don't instruct adults I do instruct kids in sewing, crafts etc., anyone that shows up late has to catch up. we do not stop the class for them