Specific
aspects
that
positively
correlated
with
gains
included
teacher-‐directed
instruction
and
small-‐group
instruction,
but
provision
of
additional
services
tended
to
be
associated
with
negative
gains.
A
host
of
original
and
synthetic
studies
have
found
positive
effects
for
a
range
of
outcomes,
and
this
pattern
is
clearest
for
outcomes
relating
to
cognitive
development.