A school document that records a student's grades, attendance, and teacher comments. Commonly used in elementary through high school contexts.
学期末に通信簿をもらった。
I received my report card at the end of the term.
通信簿の成績が上がって嬉しい。
I'm happy that my grades on the report card went up.
通信網 (a communications network) and 通信簿 (a school report card) share the kanji 通信 but refer to completely unrelated things.
Compound of 通信 (つうしん, 'communication') and 簿 (ぼ, 'record book'). The term reflects its function as a booklet for communicating a student's progress between school and home.