 ARM I: Patients receive MTX IT on days 1, 8, 15, and 22; cyclophosphamide IV over 30 minutes on days 1 and 29; cytarabine IV over 15-30 minutes or subcutaneously SC on days 1-4, 8-11, 29-32, and 36-39; mercaptopurine PO on days 1-14 and 29-42; vincristine sulfate IV on days 15, 22, 43 and 50; and pegaspargase IM or IV over 1-2 hours on days 15 and 43. Patients with persistent testicular disease or with DS and testicular disease undergo testicular radiotherapy on days 11-12, 15-19, and 22-26 DS patients excluded as of 092910. Patients with intermediate-risk or high-risk disease CNS1 or CNS2 undergo prophylactic cranial radiotherapy CRT 1,200 cGydose once daily on days 15-21 and 22-28. Patients with low-risk disease do not undergo CRT. 