DES MOINES, Iowa (AP) — An Iowa teen who pleaded guilty to beating his high school Spanish teacher to death with a baseball bat must serve 35 years in prison before the possibility of parole, the state’s high court reaffirmed Friday.

Willard Miller was 16 when he and another teen killed Nohema Graber, a 66-year-old teacher at Fairfield High School, in 2021. Miller was sentenced last year to life in prison with a mandatory minimum number of years served, but he appealed his sentence to the Iowa Supreme Court, arguing it’s unconstitutional to sentence juvenile offenders to a minimum term before parole eligibility.

The state Supreme Court on Friday unanimously upheld the district court’s decision, finding that the court’s precedent explicitly allows mandatory minimums for juvenile offenders so long as the unique factors of their case are considered. The justices said the district court judge applied sentencing factors appropriately.

The Iowa Constitution does, however, prohibit sentencing juvenile offenders to life without the possibility of parole.

Miller and Jeremy Goodale, who was sentenced to life in prison with parole eligibility after 25 years, killed Graber on Nov. 2, 2021, in a park where the teacher routinely walked after school. Prosecutors said the teens were angry at Graber because of a bad grade she had given Miller.

The two were charged as adults, but because of their age they were not subject to a mandatory sentence of life without parole for first-degree murder.

At his sentencing hearing, Miller accepted responsibility and apologized. His lawyers argued he should be eligible for immediate parole. Lawyers for the state recommended a minimum of 30 years.

Fairfield, a city of 9,400 people, is about 100 miles (160 kilometers) southeast of Des Moines.