The Saginaw Valley League will expand from 10 to 15 schools.
The SVL added the remaining four members of the former Big 9 Conference and also accepted former member Flint Northwestern.
The expansion will happen before the 2012-13 school year begins.
The league will split into two divisions, north and south.
The North Division consists of Saginaw Heritage, Saginaw Arthur Hill, Saginaw High, Bay City Central, Bay City Western, Midland High, Midland Dow and Mt. Pleasant.
The South Division will consist of Flint Northwestern, Flint Southwestern Academy, Flint Northern, Flint Powers, Flint Carmen-Ainsworth, Davison, and Flushing.