Brenden Bridges, 18, and Adam Staup, 17, will be sentenced together in front of a judge.
They admitted killing 17-year-old Wylie East High School student Ivan Mejia in March of last year.
Police said they lured Mejia to the school parking lot and then strangled him. Officers caught them trying to bury the body in a remote area near Firewheel Mall.
According to prosecutors, the pair planned the murder for five days because Bridges had feelings for Mejia's girlfriend.
Bridges allegedly told friends, "I want Ivan out of the way so I can be with her. You don't understand, sometimes I want to kill him," and "It would be easier if Ivan was out of the picture. Ivan is dead to me."
A judge will hear testimony from character witnesses before deciding on a sentence.
The state has suggested they get life in prison, but defense attorneys think 20 years would be more appropriate.
Bridges and Staup are being tried as adults.