 ARM I: Patients receive vincristine sulfate IV on days 1, 8, 15, 43, and 50; dexamethasone IV or PO BID on days 1-21 for patients 10 years of age OR on days 1-7 and 15-21 for patients 10 years of age and for patients with DS; doxorubicin hydrochloride IV over 1-15 minutes on days 1, 8, and 15; pegaspargase IM or IV over 1-2 hours on day 4, 5, OR 6, AND day 43; MTX IT on days 1, 29, and 36; cyclophosphamide IV over 30 minutes on day 29; cytarabine IV over 15-30 minutes or SC on days 29-32 and 36-39; and thioguanine PO on days 29-42. Patients with DS also receive leucovorin calcium PO at 48 and 60 hours after each methotrexate dose DS patients excluded as of 092910. 