3 Genders

I think there should be 3 gender classes:

1. Males, neutered or intact.

2. Neutered males & spayed females.

3. Females, spayed or whole.

If the dogs are divided into four groups, people with puppies will have to join a different play group if they have their dog fixed.

Three genders works better than four.

A person with a neutered male can arrive in time for all males, and stay for all fixed dogs;
a person with a spayed female can arrive for all fixed dogs, and stay for all females.

Not all people want to take their neutered dogs in to a dog park or obedience ring that has unfixed males in it.