 ARM II: Patients receive nelarabine IV over 60 minutes on days 1-5 and 43-47; MTX IT on days 15, 22, 57, and 64; cyclophosphamide IV over 30 minutes on days 8 and 50; cytarabine IV over 15-30 minutes or SC on days 8-11, 15-18, 50-53 and 57-60; oral mercaptopurine on days 8-21 and 50-63; vincristine sulfate IV on days 22, 29, 64, and 71; and pegaspargase IM or IV over 1-2 hours on days 22 and 64. Patients with persistent testicular disease or with DS and testicular disease undergo testicular radiotherapy on days 15, 22-26, and 29-33 DS patients excluded as of 092910. Patients with intermediate-risk or high-risk disease CNS1 or CNS2 undergo prophylactic CRT once daily on days 22-28 and 29-35. 