This is an investigational study. Clofarabine is FDA approved and commercially available to treat acute lymphoblastic leukemia (ALL) in children. Idarubicin and cytarabine are FDA approved and commercially available to treat acute myeloid leukemia (AML). Rituximab is FDA approved and commercially available to treat various types of lymphoma and leukemia. The use of these drugs in combination with vincristine and dexamethasone to treat mixed phenotype acute leukemia is investigational.