HIGH-redshift radio galaxies are characterized by ultraviolet excesses1,2 associated with elongated continuum and emission-line structures aligned along their radio axes3,4. Commonly, these properties are interpreted in terms of jet-induced star formation. However, observations of a blue, polarized continuum knot in the low-redshift radio galaxy PKS2152 - 69 have suggested an alternative beaming/scattering model5,6. To test this model we have obtained imaging-polarimetry observations of two high-redshift radio galaxies: 3C277.2 (z = 0.766) and 3C368 (z = 1.132). We find that both sources are strongly linearly polarized at ultraviolet rest wavelengths, with E-vectors within 25° of perpendicular to the axis of the extended continuum and radio structures. This implies that a large proportion of the ultraviolet light in these objects does not come directly from stars and we suggest it is scattered radiation from the nucleus. These observations also have important implications for beaming models of the active nuclei and for our understanding of the evolution of the host galaxies.