Additional Study Information: The purpose of this study is to find the best dose of Palbociclib that can be given safely with chemotherapy in children and young adults with Acute Lymphoblastic Leukemia (ALL) or Lymphoblastic Lymphoma (LL) which has come back or has not responded to standard therapy. Palbociclib is considered experimental because it has not been approved by the United States (US) Food and Drug Administration (FDA) for treating children with Acute Lymphoblastic Leukemia (ALL) and Lymphoblastic Lymphoma (LL). Palbociclib works by targeting proteins that are necessary for cell growth. Palbociclib is given by mouth once daily for the first 21 days of the 32-day cycle. It will be given in combination with standard chemotherapy.