Another goal of the study to learn how vitamin D levels relate to bone problems (such as broken bones or fractures) that children and adolescents with ALL and lymphoblastic lymphoma experience while on treatment. Some of the chemotherapy drugs used to treat ALL and lymphoblastic lymphoma can make bones weaker, which make fractures more likely. Vitamin D is a natural substance from food and sunlight that can help keep bones strong. The investigators will study how often participants have low levels of vitamin D while receiving chemotherapy, and, for those with low levels, whether giving vitamin D supplements will increase those levels.