SOLVED. Children's/ YA book. Boy sent to juvie/ correctional facility after killing his friend who stole his uncle's purple heart medal. Read in early 2010's. Spoilers ahead. [s]

[Jayden]

A boy is in some sort of juvie/correctional/mental health facility after pushing his friend into a pit and killing him after his friend stole his uncle's purple heart. At the end of the book the boy went and apologized to his friend's parents for killing him. The main character had initials that followed the alphabet, I think RST, and at the end of the book his baby sister was born and he gave her the same initials. There was also a girl who was a teacher's pet with the initials ABC.

[Becca]

The End of the Line by Angela Cerrito. You're right, the boy's name is Robbie Sander Thompson (RST). There's a copy on archive.org if you need to double-check: https://archive.org/details/endofline...

[Jayden]

Becca wrote: "The End of the Line by Angela Cerrito. You're right, the boy's name is Robbie Sander Thompson (RST). There's a copy on archive.org if you need to double-check: https://archive.org/de..."
This was it! Thank you!