COLUMBIA, S.C. (AP) — A South Carolina school shooting will soon become a test case for court rulings that restrict life-without-parole sentences for juveniles, after a 16-year-old pleaded guilty to two counts of murder.

Jesse Osborne pleaded guilty earlier this month to two charges of murder for fatally shooting his father in their home and a 6-year-old boy at the South Carolina elementary school Osborne once attended.

Prosecutors said they would seek a life sentence without parole. Osborne faces a minimum of 30 years.

The U.S. Supreme Court rejected mandatory life without parole for juvenile...