Different Story #2: High school theme, ch. 1

Based slightly on TheLedBalloon's story. I liked my fantasy one, and maybe I'll come back to it. I guess what I'm doing could be called "Character experiments."

Alex looked out over the empty parking lot in front of his school. What a start to his freshman year, he thought. He had been sent to detention for the third time in as many weeks. Sitting in a quiet room doing nothing didn't bore him, though.
This detention was different from the others. They let him listen to his ipod, but he chose not to this time. The stillness and the quiet with the three other detention regulars was soothing. His personality, in that short time in there, seemed to have changed.
Alex started walking across the long, boiling hot blacktop of the parking lot in the general direction of his house. His thoughts didn't have a specific content, they were focused on the heat lines off in the distance, the kind that distorted what was ahead of him.
In the quiet stillness, he didn't worry about his future anymore. He stopped worrying about his folks and his family. He stopped worrying about his grades. There was nothing but the room and him, and it didn't feel like a hostile relationship. Suddenly, in the classroom, he could feel his emotions receding from him, like blood from a heart.
Maybe it hadn't happened so suddenly. As his parents' fights had gotten worse and worse, and as he became more and more "rambunctious," he could feel emotions slipping away from him. He was getting caught less and less now, maybe because he was becoming harder to read. He didn't feel anxious about walking home, now. He didn't know what he felt.
As he was walking, Alex stared at his feet and looked at the cracks in the asphalt. That one looked like a triangle. That one looked like a spiderweb. The shapes started coalescing, and he couldn't keep them straight anymore. He wasn't sure why, but he noticed his fists were clenched, and his teeth were barred. He didn't feel angry, but he could tell that he was.
Alex left the parking lot and started down the sidewalk to his house. It was a middle class neighborhood, maybe on the verge of poverty. He was the youngest in his family, and was expected to be the peacemaker whenever his parents started fighting, or at least, that's what he felt. His two older siblings just left the house with their respective friends, and seemed in denial about what was happening.
Why did they leave him alone with his parents? He wondered. He could feel a clenching in his throat, and his eyes squeezing together, but the feeling passed. He stared at his house, and he felt something: terror. There was only one car in the driveway where once there were two. This feeling of terror grabbed him, and Alex ran inside. He knew that his dad never worked this late, and that mom wasn't allowed to drive that car.
In the kitchen was his mother, slowly washing dishes by the yellow light of a skylight overhead. Alex watched her silently, and he knew she must have heard him, but there were other things on her mind now. Alex failed, and he knew it: he couldn't save his mom and dad.
Flashing in his mind now were new thoughts. Exciting thoughts. Usually excitement meant a sudden fight had broken out between his parents and had woken him up from sleep, but this kind of excitement was different. It wasn't a sympathetic "oh I have to do something" feeling: These thoughts, he could tell, resided in the sadistic side of the spectrum. He had to do something, all right, but to whom?