 ARM III: Patients receive vincristine sulfate, dexamethasone, mercaptopurine, methotrexate PO, and methotrexate IT as in arm I. Treatment repeats every 84 days until the total duration of study treatment is 2 years from the start of interim maintenance therapy approximately week 119 for girls with T-ALL and 3 years from the start of interim maintenance therapy approximately week 171 for boys with T-ALL. 