Another part of the study is to determine whether giving antibiotics during the first month of treatment even to participants without fever will prevent serious infections in the blood and other parts of the body. About 25% of children and adolescents with ALL and lymphoblastic lymphoma who receive standard treatment develop a serious blood infection from a bacteria during the first month of treatment. Typically, antibiotics (medicines that fight bacteria) are given by vein only after a child with leukemia or lymphoma develops a fever or have other signs of infection. In this study, antibiotics will be given by mouth or in the vein to all participants during the first month of treatment, whether or not they develop fever.