hi i to work the same as you but i havent met this problem yet, but i do know that they need sexual education, how to relive them self etc. Maybe look into sex educ for autistic and look into Torey hayden i think she has the answer to your question and the experience !!! the autistic boy i work with are both 8 years old and so far they re ok. Maybe too you should talk to who ever you work for because some time those guys need a man, it s possible that being in your company might mess with their hormons! this could actually be true, in my school i ve a 13 years old mentally retarded who can not function when around women !!!
This type of behavior is sometimes connected. I have found that in setting his routine for each day,let him play in the shower. Support this by giving him praise because he observed the house rules. Make sure you tell him he may only show this type of behavior in the bathroom or in private as in bed. Each time he behaves improperly, you must tell him that he broke the house rule and take away something he loves to do...with exception of things he must use 2 hands for ;-)
Sincerely,
MENTOR4SUCCES