  We give a priori error estimates of second order in time fully explicit
Runge-Kutta discontinuous Galerkin schemes using upwind fluxes to smooth
solutions of scalar fractional conservation laws in one space dimension. Under
the time step restrictions $\tau\leq c h$ for piecewise linear and
$\tau\lesssim h^{4/3}$ for higher order finite elements, we prove a convergence
rate for the energy norm
$\|\cdot\|_{L^\infty_tL^2_x}+|\cdot|_{L^2_tH^{\lambda/2}_x}$ that is optimal
for solutions and flux functions that are smooth enough. Our proof relies on a
novel upwind projection of the exact solution.
