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