  We present results for the large-$p_T$ inclusive $\pi^0$ production in p-p
and A-A collisions at RHIC and LHC energies. We include the full
next-to-leading order radiative corrections, $O(\alpha_s^3)$, and nuclear
effects such as parton energy loss and nuclear shadowing. We find the
next-to-leading order corrections and the parton energy loss effect to be large
and $p_T$ dependent, while the nuclear shadowing effects are small ($< 10%$).
We calculate the ratio of prompt photons to neutral pions produced in heavy ion
collisions and show that at RHIC energies this ratio increases with $p_T$
approaching one at $p_T \sim 8$ GeV, due to the large suppression of $\pi^0$
production. We show that at the LHC, this ratio has a steep $p_T$ dependence
and approaches 25% effect at $p_T \sim 40$ GeV. We discuss theoretical
uncertainties inherent in our calculation, such as choice of the
renormalization, factorization and fragmentation scales and the K-factors which
signify the size of higher-order corrections.
