Reduced Craniospinal Radiation Therapy and Chemotherapy in Treating Younger Patients With Newly Diagnosed WNT-Driven Medulloblastoma

Inclusion Criteria: * Patients must be greater than or equal to 3 years and less than 22 years of age at the time of enrollment * Patients must be newly diagnosed and have: * Eligibility confirmed by rapid central pathology and molecular screening review on APEC14B1: * Classical histologic type (non LC/A) WNT medulloblastoma * Positive nuclear beta-catenin by immunohistochemistry (IHC) * Positive for CTNNB1 mutation by Sanger sequencing * Negative for MYC and MYCN by fluorescence in situ hybridization (FISH) * Patient must have negative lumbar cerebrospinal fluid (CSF) cytology * Note: CSF cytology for staging should be performed no sooner than 14 days post operatively to avoid false positive CSF; ideally, CSF should be obtained between day 14 and day 21 to allow for final staging status before enrollment onto the study; patients with positive CSF cytology obtained 0 to 14 days after surgery should have cytology repeated to determine eligibility and final CSF status; patients with negative CSF cytology from lumbar puncture obtained 0 to 14 days after surgery do not need cytology repeated; patients with negative CSF cytology from lumbar puncture obtained prior to surgery do not need cytology repeated post-operatively * Patients must have eligibility confirmed by Rapid Central Imaging Review on APEC14B1; patients must have =\< 1.5 cm\^2 maximal cross-sectional area of residual tumor; whole brain magnetic resonance imaging (MRI) with and without gadolinium and spine MRI with gadolinium must be performed * Patients must be enrolled, and protocol therapy must be projected to begin, no later than 36 days after definitive diagnostic surgery (day 0) * Peripheral absolute neutrophil count (ANC) \>= 1000/uL * Platelet count \>= 100,000/uL (transfusion independent) * Hemoglobin \>= 8.0 g/dL (may receive red blood cell \[RBC\] transfusions) * Creatinine clearance or radioisotope glomerular filtration rate (GFR) \>= 70 mL/min/1.73 m\^2 or a serum creatinine based on age/gender as follows: * 3 to \< 6 years of age: maximum (max) serum creatinine 0.8 mg/dL (males and females) * 6 to \< 10 years of age: max serum creatinine 1 mg/dL (males and females) * 10 to \< 13 years of age: max serum creatinine 1.2 mg/dL (males and females) * 13 to \< 16 years of age: max serum creatinine 1.5 md/dL (males) and 1.4 md/dL (females) * \>= 16 years of age: max serum creatinine 1.7 mg/dL (males) and 1.4 mg/dL (females) * The threshold creatinine values were derived from the Schwartz formula for estimating GFR utilizing child length and stature data published by the Centers for Disease Control and Prevention (CDC) * Total or direct bilirubin =\< 1.5 x upper limit of normal (ULN) for age, and * Serum glutamate pyruvate (SGPT) (alanine aminotransferase \[ALT\]) =\< 135 U/L (3x ULN); for the purpose of this study, the ULN for SGPT is 45 U/L * Central nervous system function defined as: * Patients with seizure disorder may be enrolled if on anticonvulsants and well controlled * Patients must not be in status epilepticus, a coma or on assisted ventilation at the time of study enrollment * Patients must have receptive and expressive language skills in English, French, or Spanish to complete the QoL and neurocognitive assessments; if a patient meets these criteria but the parent/guardian speaks a language other than English, French, or Spanish, the patient may still be enrolled and tested, and the parent-report measures should be omitted * All patients and/or their parents or legal guardians must sign a written informed consent; assent, when appropriate, will be obtained according to institutional guidelines * All institutional, Food and Drug Administration (FDA), and National Cancer Institute (NCI) requirements for human studies must be met Exclusion Criteria: * Patients with metastatic disease by either MRI evaluation (brain and spine) or lumbar CSF cytology are not eligible; patients who are unable to undergo a lumbar puncture for assessment of CSF cytology are ineligible * Patients must not have received any prior radiation therapy or chemotherapy (tumor-directed therapy) other than surgical intervention and/or corticosteroids * Pregnancy and Breast Feeding * Female patients who are pregnant are ineligible due to risks of fetal and teratogenic adverse events as seen in animal/human studies * Lactating females are not eligible unless they have agreed not to breastfeed their infants * Female patients of childbearing potential are not eligible unless a negative pregnancy test result has been obtained * Sexually active patients of reproductive potential are not eligible unless they have agreed to use an effective contraceptive method for the duration of their study participation * Patients with a history of moderate to profound intellectual disability (i.e., intelligence quotient \[Q)\]=\< 55) are not eligible for enrollment; PLEASE NOTE: Children with a prior history of attention deficit hyperactivity disorder (ADHD) or a specific learning disability (e.g., dyslexia) are eligible for this study. Children with posterior fossa syndrome (also known as cerebellar mutism) are eligible for this study