Selumetinib vs Carboplatin and Vincristine for Low-Grade Glioma

Inclusion Criteria: * Patients must be \>= 2 years and =\< 21 years at the time of enrollment * Patients must have a body surface area (BSA) of \>= 0.5 m\^2 at enrollment * Patients must have non-neurofibromatosis type 1 (non-NF1) low-grade glioma (LGG) without a BRAFV600E mutation as confirmed by Rapid Central Pathology and Molecular Screening Reviews performed on APEC14B1 (NCT02402244) Childhood Cancer Data Initiative (CCDI)-MCI, or accepted Clinical Laboratory Improvement Act (CLIA)-certified test and that has not been treated with any modality besides surgery. Note: Patients may be newly-diagnosed OR previously diagnosed, and there is no required time frame between biopsy/surgery and treatment initiation. * Patients with residual tumor after resection or progressive tumor after initial diagnosis (with or without surgery) who have not received treatment (chemotherapy and/or radiation) are eligible * Patients must have two-dimensional measurable tumor \>= 1 cm\^2 to be eligible * Patients with ependymoma are not eligible * Eligible histologies will include all tumors considered low-grade glioma or low-grade astrocytoma (World Health Organization \[WHO\] grade I and II) by 5th edition WHO classification of central nervous system (CNS) tumors with the exception of subependymal giant cell astrocytoma * Patients with metastatic disease or multiple independent primary LGG are eligible * Creatinine clearance or radioisotope glomerular filtration rate (GFR) \>= 70 mL/min/1.73 m\^2 OR a serum creatinine based on age/sex as follows (performed within 7 days prior to enrollment): * Age: Maximum Serum Creatinine (mg/dL) * 2 to \< 6 years: 0.8 mg/dL (male); 0.8 mg/dL (female) * 6 to \< 10 years: 1 mg/dL (male); 1 mg/dL (female) * 10 to \< 13 years: 1.2 mg/dL (male); 1.2 mg/dL (female) * 13 to \< 16 years: 1.5 mg/dL (male); 1.4 mg/dL (female) * \>= 16 years: 1.7 mg/dL (male); 1.4 mg/dL (female) * Total bilirubin =\< 1.5 x upper limit of normal (ULN) for age (performed within 7 days prior to enrollment) (children with a diagnosis of Gilbert's syndrome will be allowed on study regardless of their total and indirect \[unconjugated\] bilirubin levels as long as their direct \[conjugated\] bilirubin is \< 3.1 mg/dL) * Serum glutamic pyruvic transaminase (SGPT) (alanine aminotransferase \[ALT\]) =\< 135 U/L (performed within 7 days prior to enrollment). For the purpose of this study, the ULN for SGPT is 45 U/L * Albumin \>= 2 g/dL (performed within 7 days prior to enrollment) * Left ventricular ejection fraction (LVEF) \>= 53% (or institutional normal; if the LVEF result is given as a range of values, then the upper value of the range will be used) by echocardiogram (performed within 4 weeks prior to enrollment) * Corrected QT (QTc) interval =\< 450 msec by electrocardiography (EKG) (performed within 4 weeks prior to enrollment) * Absolute neutrophil count \>= 1,000/uL (unsupported) (performed within 7 days prior to enrollment) * Platelets \>= 100,000/uL (unsupported) (performed within 7 days prior to enrollment) * Hemoglobin \>= 8 g/dL (may be supported) (performed within 7 days prior to enrollment) * Patients with a known seizure disorder must be stable and must not have experienced a significant increase in seizure frequency within 2 weeks prior to enrollment * Patients 2-17 years of age must have a blood pressure that is =\< 95th percentile for age, height, and sex at the time of enrollment (with or without the use of anti-hypertensive medications) * Patients \>= 18 years of age must have a blood pressure =\< 130/80 mmHg at the time of enrollment (with or without the use of anti-hypertensive medications) * Note for patients of all ages: Adequate blood pressure can be achieved using medication for the treatment of hypertension * All patients must have ophthalmology toxicity assessments performed within 8 weeks prior to enrollment * For all patients, an MRI of the brain (with orbital cuts for optic pathway tumors) and/or spine (depending on the site(s) of primary disease) with and without contrast must be performed within 8 weeks prior to enrollment * Patients must have a performance status corresponding to Eastern Cooperative Oncology Group (ECOG) scores of 0, 1, or 2. Use Karnofsky for patients \> 16 years of age and Lansky for patients =\< 16 years of age * Patients must have the ability to swallow whole capsules * All patients and/or their parents or legal guardians must sign a written informed consent * All institutional, Food and Drug Administration (FDA), and National Cancer Institute (NCI) requirements for human studies must be met * All patients have signed an appropriate consent form and Health Insurance Portability and Accountability Act (HIPAA) authorization form (if applicable) * All patients have been consented and enrolled on APEC14B1 (NCT02402244) Part A for Pre-Enrollment Eligibility Screening for ACNS1833 Exclusion Criteria: * Patients must not have received any prior tumor-directed therapy including chemotherapy, radiation therapy, immunotherapy, or bone marrow transplant. Prior surgical intervention (with the exclusion of laser interstitial thermal therapy \[LITT\]) is permitted * Patients with a concurrent malignancy or history of treatment (other than surgery) for another tumor within the last year are ineligible * Patients with diffuse intrinsic pontine tumors as seen on MRI (\> 2/3 of pons involvement on imaging) are not eligible even if biopsy reveals grade I/II histology * Patients may not be receiving any other investigational agents * Patients with any serious medical or psychiatric illness/condition, including substance use disorders or ophthalmological conditions, likely in the judgment of the investigator to interfere or limit compliance with study requirements/treatment * Patients who, in the opinion of the investigator, are not able to comply with the study procedures are not eligible * Female patients who are pregnant are not eligible since fetal toxicities and teratogenic effects have been noted for several of the study drugs. A pregnancy test is required for female patients of childbearing potential * Lactating females who plan to breastfeed their infants are not eligible * Sexually active patients of reproductive potential who have not agreed to use an effective contraceptive method for the duration of their study participation and for 1 week after stopping study therapy are not eligible. * Note: Women study participants of child-bearing potential must use acceptable contraception during the study and for 1 week (7 days) after the last dose of selumetinib. Men study participants with sexual partners who are pregnant or who are of child-bearing potential must use acceptable contraception during the study and for 1 week (7 days) after the last dose of study agent. Acceptable contraception includes implants, injectables, or oral contraceptives (all combined with barrier methods), some intrauterine devices (IUDs), vasectomy or abstinence * Known genetic disorder that increases risk for coronary artery disease. Note: The presence of dyslipidemia in a family with a history of myocardial infarction is not in itself an exclusion unless there is a known genetic disorder documented * Symptomatic heart failure * New York Health Association (NYHA) class II-IV prior or current cardiomyopathy * Severe valvular heart disease * History of atrial fibrillation * Current or past history of central serous retinopathy * Current or past history of retinal vein occlusion or retinal detachment * Patients with uncontrolled glaucoma * If checking pressure is clinically indicated, patients with intraocular pressure (IOP) \> 22 mmHg or ULN adjusted by age are not eligible * Supplementation with vitamin E greater than 100% of the daily recommended dose. Any multivitamin containing vitamin E must be stopped prior to study enrollment even if less than 100% of the daily recommended dosing for vitamin E * Surgery within 2 weeks prior to enrollment, with the exception of surgical biopsy, placement of a vascular access device or cerebral spinal fluid (CSF) diverting procedure such as endoscopic third ventriculostomy (ETV) and ventriculoperitoneal (VP) shunt. * Note: Patients must have healed from any prior surgery * Patients who have an uncontrolled infection are not eligible