Middle school application process

Hi all, we're expecting a baby soon so we've been shopping around for a co-op. One of the addresses we're interested in doesn't have a zoned middle school. It's in District 3, however. How does this affect the middle school application process? I don't know much about the process to begin with. I heard it's pretty much a lottery system with priority given to students living in the district of the school? All the other addresses we've looked at had a zoned middle school, but oddly this one doesn't.