This phase II trial studies how well lower dose radiotherapy after chemotherapy (Carboplatin \& Etoposide) works in treating children with central nervous system (CNS) germinomas. Radiation therapy uses high energy x-rays, particles, or radioactive seeds to kill cancer cells and shrink tumors. Carboplatin is in a class of medications known as platinum-containing compounds. It works in a way similar to the anticancer drug cisplatin, but may be better tolerated than cisplatin. Carboplatin works by killing, stopping or slowing the growth of tumor cells. Etoposide is in a class of medications known as podophyllotoxin derivatives. It blocks a certain enzyme needed for cell division and DNA repair and may kill cancer cells. Researchers want to see if lowering the dose of standard radiotherapy (RT) after chemotherapy can help get rid of CNS germinomas with fewer long-term side effects.