  For an action of a discrete group $\Gamma$ on a set $X$, we show that the
Schreier graph on $X$ is property A if and only if the permutation
representation on $\ell_2X$ generates an exact $\mathrm{C}^*$-algebra. This is
well known in the case of the left regular action on $X=\Gamma$. This also
generalizes Sako's theorem, which states that exactness of the uniform Roe
algebra $\mathrm{C}^*_{\mathrm{u}}(X)$ characterizes property A of $X$ when $X$
is uniformly locally finite.
