Chemotherapy (treatment with anti-cancer drugs) will be given as part of treatment for participants whose tumors are not completely removed surgically. Participants in one group will receive carboplatin plus etoposide, vincristine, and radiation therapy . Participants in the other group will receive cyclophosphamide plus etoposide, vincristine, and radiation therapy. Among all the known drugs for cancer, etoposide, vincristine, cyclophosphamide, and platinum drugs are the most effective against brain tumors. Carboplatin will be used because fewer side effects related to hearing should occur later on. This study also uses radiation therapy after surgery for children younger than 3 years old. Normally, chemotherapy has been used to delay radiation therapy until the child was older because of concerns about side effects. This change has been made because of the poor results achieved when chemotherapy was used to delay radiation therapy.