The overarching objective of this study is to use novel precision medicine strategies based on inherited and acquired leukemia-specific genomic features and targeted treatment approaches to improve the cure rate and quality of life of children with acute lymphoblastic leukemia (ALL) and acute lymphoblastic lymphoma (LLy). Primary Therapeutic Objectives: - To improve the event-free survival of provisional standard- or high-risk patients with genetically or immunologically targetable lesions or minimal residual disease (MRD) ≥ 5% at Day 15 or Day 22 or ≥1% at the end of Remission Induction, by the addition of molecular and immunotherapeutic approaches including tyrosine kinase inhibitors or chimeric antigen receptor (CAR) T cell / blinatumomab for refractory B-AL or B-LLy, and the proteasome inhibitor bortezomib for those lacking targetable lesions. - To improve overall treatment outcome of T-ALL and T-LLy by optimizing pegaspargase and cyclophosphamide treatment and by the addition of new agents in patients with targetable genomic abnormalities (e.g., activated tyrosine kinases or JAK/STAT mutations) or by the addition of bortezomib for those who have a poor early response to treatment but no targetable lesions, and by administering nelarabine to T-ALL and T-LLy patients with leukemia/lymphoma cells in cerebrospinal fluid at diagnosis or MRD ≥0.01% at the end of induction. - To determine in a randomized study design whether the incidence and/or severity of acute vincristine-induced peripheral neuropathy can be reduced by decreasing the dosage of vincristine in patients with the high-risk CEP72 TT genotype or by shortening the duration of vincristine therapy in patients with the CEP72 CC or CT genotype. Secondary Therapeutic Objectives: - To estimate the event-free survival and overall survival of children with ALL and LLy. - To determine the tolerability of combination therapy with ruxolitinib and Early Intensification therapy in patients with activation of JAK-STAT signaling that can be inhibited by ruxolitinib and Day 15 or Day 22 MRD ≥5%, Day 42 MRD ≥1%, or LLy patients without complete response at the End of Induction and all patients with early T cell precursor leukemia. Biological Objectives: - To use data from clinical genomic sequencing of diagnosis, germline/remission and MRD samples to guide therapy, including incorporation of targeted agents and institution of genetic counseling and cancer surveillance. - To evaluate and implement DNA and RNA sequencing-based methods to monitor levels of MRD in bone marrow, blood, and cerebrospinal fluid. - To assess clonal diversity and evolution of pre-leukemic and leukemic populations using DNA variant detection and single-cell genomic analyses in a non-clinical, research setting. - To identify germline or somatic genomic variants associated with drug resistance of ALL cells o conventional and newer targeted anti-leukemic agents in a non- clinical, research setting. - To compare drug sensitivity of ALL cells from diagnosis to relapse in vitro and in vivo and determine if acquired resistance to specific agents is related to specific somatic genome variants that are not detected or found in only a minor clone at initial diagnosis. Supportive Care Objectives - To conduct serial neurocognitive monitoring of patients and to evaluate the benefits of a computer-based cognitive intervention. - To evaluate the impact of low-magnitude high frequency mechanical stimulation on bone mineral density and markers of bone turnover. Exploratory Objectives: - To identify pharmacogenetic, pharmacokinetic and pharmacodynamic predictors of treatment outcome. - To perform a detailed assessment of thiopurine metabolism and 6-mercaptopurine (6MP) tolerance, toxicity, and treatment outcome. - To establish xenografts of representative subtypes of ALL. - To prospectively determine the risk and epidemiology of breakthrough infection or febrile neutropenia and adverse effects of antibiotics. - To use cell phenotyping and genomic approaches to characterize the non-tumor microenvironment and correlate with responses to conventional and immunotherapeutic approaches.