INTENSIFICATION BLOCK 1 THERAPY: (weeks 15-23) Patients receive high-dose methotrexate IV continuously over 24 hours on day 1; leucovorin calcium PO or IV every 6 hours for 3 doses on days 2-3; methotrexate, hydrocortisone, and cytarabine IT on days 1 and 22; etoposide IV over 1 hour and cyclophosphamide IV over 1 hour on days 22-26; cytarabine IV over 3 hours every 12 hours for 4 doses on days 43 and 44; asparaginase IM on day 44; and dasatinib PO on days 1-14, 22-35, and 43-56 OR on days 1-63. Patients also receive G-CSF SC or IV QD beginning on day 27 and continuing until blood counts recover. After completion of intensification block 1 therapy, patients proceed to reinduction block 2 therapy.