This pilot phase II trial studies the side effects of azacitidine and combination chemotherapy in infants with acute lymphoblastic leukemia and KMT2A gene rearrangement. Drugs used in chemotherapy, such as methotrexate, prednisolone, daunorubicin hydrochloride, cytarabine, dexamethasone, vincristine sulfate, pegaspargase, hydrocortisone sodium succinate, azacitidine, cyclophosphamide, mercaptopurine, leucovorin calcium, and thioguanine work in different ways to stop the growth of cancer cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Giving more than one drug may kill more cancer cells.