The Northern Illinois Big 12 Conference is a high-school athletic conference with ten high schools in northern Illinois. The conference began competing during the 2010-2011 academic year. In many respects, including membership and organization, the NI-Big 12 is much like a reboot of the old North Central Illinois Conference (NCIC).Six of the schools are former members of the North Central Illinois Conference (1929-2011), and the conference is divided into two divisions, much as the NCIC was for decades. The former NCIC schools are Geneseo, LaSalle-Peru, Sterling, Ottawa, and Rochelle. Also, there are five schools that were members of the Western Sun Conference (2007-2010). The former Western Sun Schools are DeKalb, Kaneland, Sycamore, Yorkville, and Rochelle, which left the NCIC in 2007 to join the WSC, and was thus a member of both extinct conferences.
The creation of the new conference appeared to have settled an unstable situation that existed in the NCIC since the departure of the Rochelle Hubs after winning nine consecutive NCIC (Southwest Div.) football championships. When Rochelle became a founding member of the Western Sun, the NCIC began shifting members trying to keep together a conference that was built of schools with inordinately large population variances. Whereas the NCIC schools had not all played in the same division in football for several decades, all the schools of the NIB-12 do play in the same division in all sports, regardless of the number of classes.
The NIB-12 essentially consists of the largest of the former NCIC's schools, with the smallest schools being replaced by Rochelle's new rivals from the Western Sun. The average enrollment of the NIB-12 schools in the 2014-15 school year was 1210, with the largest school being Yorkville (1650) and the smallest being Geneseo (832).
In 2013, both Dixon and Streator chose to leave the NIB-12. Streator was burdened by the greatest traveling distances in the conference, and Dixon simply proved too weak to be able to compete. With the two Western Division schools leaving, Rochelle was moved from the Eastern division to the Western, leaving both divisions with five teams.
All NIB-12 high schools are members of the Illinois High School Association (IHSA).