Let
$p$
be a prime and
$F$
a field containing a primitive
$p$
-th root of unity. Then for
$n\,\in \,\mathbb{N}$
, the cohomological dimension of the maximal pro-
$p$
-quotient
$G$
of the absolute Galois group of
$F$
is at most
$n$
if and only if the corestriction maps
${{H}^{n}}\left( H,\ {{\mathbb{F}}_{p}} \right)\,\to \,{{H}^{n}}\left( G,\ {{\mathbb{F}}_{p}} \right)$
are surjective for all open subgroups
$H$
of index
$p$
. Using this result, we generalize Schreier's formula for
${{\dim}_{{{\mathbb{F}}_{p}}}}\,{{H}^{1}}\,\left( H,\ {{\mathbb{F}}_{p}} \right)$
to
${{\dim}_{{{\mathbb{F}}_{p}}}}{{H}^{n}}\left( H,\ {{\mathbb{F}}_{p}} \right)$
.