 Patients with pediatric brain tumors medulloblastoma, CNS PNET, high grade glioma who have experienced disease relapse or progressive refractory disease will be eligible. Each cycle will consist of DAC at low dose administered over a 5 day period, followed by two weekly vaccinations consisting of autologous dendritic cells pulsed with pooled, overlapping peptide mixes derived from full-length MAGE-A1, MAGE-A3, and NY-ESO-1. This dose of DAC is lower than all previously reported doses that have been safely administered in adult patients with MDS and AML, and was used in a previous protocol for relapsed and refractory pediatric neuroblastoma and sarcomas. A novel way of stimulating CD4 and CD8 antigen specific T cells is to use a DC vaccine approach in which the cells are pulsed with overlapping peptides derived from these antigens, so that patients from several different HLA backgrounds can be enrolled. Overlapping peptide mixes derived from full-length NY-ESO-1, MAGE-A1, or MAGE-A3 have been acquired from JPT Peptide Technologies, consisting of 15-mers, with 11 amino acid overlap. The number of DC given in our study 8-10 x 106 peptide pulsed DC is within the range of doses given in previous studies. Vaccinations are spaced at weekly intervals, based on multiple previous studies in which this approach is taken, and the fact that in vitro re-stimulation of CTL generally occurs on a weekly basis. GM-CSF is given days 1 through 5 during vaccine weeks, to minimize leukopenia from DAC and to help facilitate antigen presenting cell function. The adjuvant poly-ICLC Hiltonol will be injected immediately after and adjacent to DC vaccine site to enhance DC maturation. We will accrue 10 patients with relapsed, refractory, or progressive pediatric brain tumors over a 3 year period. Cycles will repeat every five weeks, for two cycles. Patients who do not have disease progression after two cycles may receive an additional two cycles of therapy. 