Maintenance chemotherapy will be given for a total of 30 months and will be interrupted by 2 periods of intensive chemotherapy courses. For maintenance therapy, you will receive 6-mercaptopurine by mouth up to 3 times a day, methotrexate by mouth once a week, vincristine by vein once a month over a few minutes, and prednisone by mouth once a day for 5 days in a row every month. The first period of intensive chemotherapy courses will be given at Courses 6 and 7 into the maintenance program. For the intensive chemotherapy at this time, you will receive nelarabine by vein over 2 hours once a day for 5 days in a row and Pegaspargase will be given by vein over 2 hours on day 5. This will be repeated for another cycle about 21-35 days apart from each other. The second period of intensive chemotherapy courses will be given at Courses 18 and 19. It will start first with methotrexate by vein on Day 1 and pegaspargase by vein on Day 2. These will be given once a week for 4 doses. The following month, you will receive hyper-CVAD (like during Course 1 at the very beginning of treatment). The hyper-CVAD may begin before the combination of methotrexate and pegaspargase.