OBJECTIVES: I. Develop risk-adapted therapy for patients with low-risk, high-risk, T-cell, or B-cell acute lymphocytic leukemia (ALL). II. Determine the complete remission rate in these patients treated with the following strategies: increased doses of cyclophosphamide during induction and reinduction, early use of high-dose cytarabine plus mitoxantrone (for high-risk patients), and increased doses of methotrexate (for B-cell ALL patients). III. Determine the duration of remission and survival of patients in all risk groups treated with intensified consolidation and subtype-specific chemotherapy. IV. Compare the effects of intensified vs conventional maintenance therapy in patients of all risk groups.