Combination Chemotherapy Plus Steroid Therapy in Treating Children With Acute Lymphoblastic Leukemia or Lymphoblastic Non-Hodgkin's Lymphoma

RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Combining more than one drug may kill more tumor cells. It is not yet known which regimen of combination chemotherapy plus steroid therapy is more effective for acute lymphoblastic leukemia or lymphoblastic non-Hodgkin's lymphoma. PURPOSE: Randomized phase III trial to compare the effectiveness of different regimens of combination chemotherapy plus steroid therapy in treating children who have acute lymphoblastic leukemia or lymphoblastic non-Hodgkin's lymphoma.