This is completely unacceptable behavior. Moms should respect their children's privacy and not share inappropriate stories about them with friends. Such actions can cause great harm to the son, both psychologically and in terms of his reputation.
There could be many stories. Maybe it's about a mom and her friends planning a surprise party for her son. They could be decorating the house, baking a cake, and waiting for the son to come home from school to give him a wonderful surprise.
It is completely wrong. A mom has no place in teaching sex stories to her son's friends. Children need to be taught about sex in an appropriate setting, like in a school health class or by their own parents in a proper age - appropriate way. This kind of behavior from a mom can cause a lot of problems, from making the kids feel awkward to having a negative influence on their view of appropriate adult - child relationships.
Maybe they volunteered at a community garden. The mom showed the kids how to plant seeds, and the son and his friends watered the plants and pulled out weeds.
They can go on a camping trip together. During the trip, they can share stories around the campfire, cook meals together, and explore the outdoors. This will create memories that last a lifetime.
If such a situation is discovered, the authorities or child protection services should be informed immediately. This is a serious matter as it can have a negative impact on the children's mental and emotional well - being.