This randomized phase II trial studies how well giving temozolomide and irinotecan hydrochloride together with or without bevacizumab works in treating young patients with recurrent or refractory medulloblastoma or central nervous system (CNS) primitive neuroectodermal tumors. Drugs used in chemotherapy, such as temozolomide and irinotecan hydrochloride, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Monoclonal antibodies, such as bevacizumab, can block tumor growth in different ways. Some block the ability of tumor cells to grow and spread. Others find tumor cells and help kill them or carry tumor-killing substances to them. It is not yet known whether temozolomide and irinotecan hydrochloride are more effective with or without bevacizumab in treating medulloblastoma or CNS primitive neuroectodermal tumors.