Behind the scenes, both sites use the same WordPress instance and the same database. I managed to do this by using the Domain Mirror WordPress plugin. It allows a WordPress instance to be accessible from multiple domains. I could sniff out the domain requested and serve up a different header, footer and stylesheet for each of the sites.
I also sorted the jobs list on the home page of each site to favor recent jobs that are local to each site. I laid out the plans for this here. Various widgets, contact emails, featured post prices, and site copy are also unique to each site.
Hopefully this jobs board will gather momentum and will help to support the news reporting on EdNews Colorado as it is doing for GothamSchools. I also hope that partnering both sites like this will be an added incentive for people to post their listing, knowing that it will show up on both jobs boards. Perhaps in the future we can roll this out to other education news sites across the country.