Special Judge Jon Kerry Blackwood is scheduled to hear 15-year-old Kenneth Bartley's claims on Monday in Jacksboro.
"It is all the marbles in terms of what this kid is facing," said Bruce Poston, Bartley's new attorney.
Bartley claims "his plea was not made voluntarily," in his latest motion filed this week.
The youth contends "he was pressured by prior counsel (Mike Hatmaker) to accept the plea offer and was not given the opportunity to talk with anyone else, especially his parents, regarding the agreement brokered at the last minute by his counsel."
Bartley was accused of fatally shooting Assistant Principal Ken Bruce, 51, and wounding Principal Ken Seale and Assistant Principal Jim Pierce on Nov. 8, 2005, when they questioned him about whether he brought a gun to Campbell County Comprehensive High School.
Bartley, then 14, pulled out a handgun, loaded it and began firing, Pierce and Seale testified at a preliminary hearing.
As the jury was being picked for his trial on April 10, Bartley met privately with the victims and their families and then entered a surprise guilty plea to a reduced charge of second-degree murder and attempted second-degree murder.
Blackwood sentenced him to 45 years in prison. Bartley was spared a mandatory 51-year sentence if he had been convicted of first-degree murder and given the possibility of parole in about 25 years.
But Bartley soon after filed a motion to withdraw the plea, saying Blackwood accepted it without a formal admission of facts and without the consent of his parents. Then, in May, he fired Hatmaker and hired Poston of Knoxville.