Attenuation of neutrons and photons transmitted through graphite, iron, water, and ordinary concrete assemblies were studied by spectral measurements using an NE-213 organic scintillation detector with an (n-γ) discrimination technique. Source neutrons and photons were produced by 52-MeV proton bombardment of a 21.4-mm-thick graphite target placed in front of the assembly. The distributions of the light output from the scintillator following activation by neutrons and photons were unfolded by the revised FERDO code. These experimental results were used as benchmark data on neutron and photon penetration by neutrons of energy above 15 MeV. Multigroup Monte Carlo and one-dimensional ANISN transport calculations were performed with the DLC-58/HELLO group cross sections to compare with the measurement and to evaluate the cross sections. The results of the ANISN calculation of neutrons in slab geometry and the three-dimensional Monte Carlo calculation agreed with the experimental values except for high energy neutrons transmitted through water and graphite. The agreement of both calculations was well within the accuracy of 7% in the measured attenuation coefficients for graphite, iron, and water, and <10% for concrete. For photons, the ANISN calculation gave >20% over-estimation of the attenuation coefficients in the case of deep penetration through the medium for which the photon mean-free-path is shorter than that of neutrons, such as in iron and concrete. The secondary photons produced by the neutron-nucleus reactions are dominant compared with the primary photons, but otherwise the ANISN calculations gave good results.