FAIRFIELD, Iowa—Two southeastern Iowa teenagers pleaded not guilty Monday to killing their high school Spanish teacher, whose body was found earlier this month in a park where she took daily walks. Willard Noble Chaiden Miller and Jeremy Everett Goodale, both 16, are charged with first-degree murder and conspiracy to commit murder in the killing Nohema Graber in Fairfield. Graber, 66, was reported missing Nov. 2 and her remains were found later that day in the local park. Authorities said she suffered “inflicted trauma to the head.” Authorities haven’t disclosed a possible motive for the killing. Miller and Goodale, who are being held in juvenile detention centers, entered their pleas in arraignment documents filed with the court Monday. They waived their right to a speedy trial, meaning prosecutors wouldn’t have to try them within 90 days of them being charged, and Judge Joel Yates scheduled the trial to begin April 19. …