Copies of Matt's poems, given to The Telegraph, refer to blood and death. One line of the poem that Matt said upset a teacher reads, "Now I got back at them/This they soon will see." Neither school nor students are explicitly mentioned.
I'm all those abstinence pledges that students in my high school signed were all upheld too. If the student is a danger than do something about it. This doesn't solve anything but seems to be a big punishment for writing that the school wanted censored.