ISU means Independent Study Unit. It is an entire unit of work that is assigned at the beginning of the semester and is due near the end of the semester. There is usually some time given in class, but, for the most part, the students must complete it independently. It is different for every subject, grade and level. Usually, in an English class, the students have to read at least one book on their own and complete a few projects, including something written (like journals or an essay), something oral (like a seminar or presentation), and something creative (like a model of something). It is different everywhere as it is up to the teacher.
Teaching In Real Life 