Minor update: At the end of the little kids' practice today, I noticed the mom (from across the pool deck) and wanted to see what she did. I watched and she went over to wait for her son to get done, and then I noticed that she was talking with the head coach for a while. After that, she wandered over by the locker rooms and (yeah!) was yelling into the locker room through the vents/slats instead of going to the door. (This is what I've been doing for years.)
So it looks like things are good for now. I, of course, will still keep an eye on it. I also learned that our president, who I contacted originally with the coach, doesn't really do anything. There is someone else, who I've known for years, and she's in the process of assuming the role. I told her about the whole situation (this was right before I saw the coach talking to the mom) and being the mother of a 16 year old boy, she was appropriately horrified when she thought of the woman walking in on her son. She turned right around and was going to ask the pool staff to put up some signs. I told her that the coach said she would talk to the mom, and she said she'd check with her first before she pursued the signs.
Thanks for all of the good discussion and back up.
May I offer a general "thank you" to you on behalf of grown men who don't want a woman walking into the men's changing room?
Years ago, when my sons were much younger, we had a YMCA membership so we could go swimming there and so the boys could take swimming lessons there.
We usually scheduled our sons' lessons for the last lesson period right before the family swimming time. A few minutes before the end ofthe lessons I would go to the men's changing room to change into my swimsuit so I could hop in the pool for family swim time.
One day, maybe fifteen or twenty seconds after I had pulled up my swimsuit, a 30 or 35 year old woman marched into the men's changing room with her 5 or 6 year old son and proceeded to help him change into his clothes.
I was upset. I tried telling her to leave, but she replied to me in a foreign language (and would not leave). I gathered up my clothing and went to complain to the manager. The woman and son had left by the time I found the manager, and I never noticed them there again.
In your case, I'm glad you helped the woman who behaved inappropriately learn to change her behavior. Your sons deserve to be able to change without a woman observing them.