Prosecutors have alleged that two Iowa teenagers who killed their high school Spanish teacher did it after they were frustrated by their poor grades, CBS News reports.

Documents filed on Tuesday allege that teens Willard Miller and Jeremy Goodale murdered 66-year-old Nohema Graber at their school in Fairfield, with evidence showing they plotted the murder due to their poor performance in Graber’s class.

A lawyer for one of the suspects has asked for four search warrants to be invalidated, as well as the suppression of evidence found in the the suspect’s home, information on his cellphone and social media, and comments he made to police.

"The poor grade is believed to be the motive behind the murder of Graber which directly connects Miller," read the court documents, filed by Jefferson County Attorney Chauncey Moulding and Assistant Iowa Attorney General Scott Brown. Miller previously denied being involved with the murder, but "later stated he had knowledge of everything but did not participate." He alleged that a "roving group of masked kids" killed Graber, and forced him to get a wheelbarrow to move her body.

Graber was found dead under a tarp in a Fairfield park on Nov. 3, 2021. The two students were 16 at the time of the murder. Evidence showed that she had been beaten to death with a baseball bat by the teens. According to investigators, Miller met with Graber to discuss his grades the day before her body was found. Witnesses saw Graber’s van leave the park, with two males in the front seats, on Nov. 2. The van was later left at the end of a nearby road. 

Photos of a Snapchat conversation apparently confirm Goodale admitted he participated in the murder of Graber. The two suspects, now 17, will be tried as adults. They are facing life in prison.