The rule was (is) that you go to your assigned congregation.
Growing up, I think our family was in our assigned congregation only one of three times. The family made two major moves when I was a kid and each time my folks would visit the various congregations in the area and pick the one with the most kids. Given our association restrictions with the world, they wanted to make sure we had plenty of friends.
I have to give them credit where due. They even stood up to an elder in one congregation who told us we didn't belong there. My dad got in his face and said THIS is where we choose to be.
And so it was.