This features a strong effort from Samuel L. Jackson but is really quite a depressing film to watch. He is "Garfield" - a teacher who survived a vicious knife attack at his previous school in New York, but who is still determined to persevere and so moves to another in Los Angeles. The teenage kids there are a pretty disparate bunch, not really interested in education and certainly not interested in authority. Except, maybe, "Rita" (Karina Arroyave) who wants to succeed despite the pressures from her peers. From the outset, "Garfield" has a challenger in the young "Cesar" (Clifton Collins…