Stagg is named after the famous football coach.
After coaching for several years at the University of Chicago, Amos Alonzo Stagg moved to Stockton and coached at the University of the Pacific, not far from the high school. Stagg Field, a football stadium in Chicago that was also named for him, was the site of the first nuclear chain reaction in 1942.
Interestingly, Stagg High school seems to be located in one of the more affluent parts of town.