Children with disadvantage often don’t do as well as others because, overall, they have had fewer resources than those who are not disadvantaged.
Schools are expected to provide additional resources to those children and indeed there is a PP payment to fund these extra resources.
However, schools that serve such communities often have to spend considerable additional (to PP) resources over and above in the form of time, effort and emotional toil.
And the end outcome will still be, overall, insufficient due to a myriad of factors - not least that it is impossible for schools to compete with parents who lavishly resource their children from birth to work and beyond to help them achieve.
The way to help schools is to provide additional resources rather than pressure staff in them to spend more of their own personal time, effort and emotional toil over and above those whose schools serve more advantaged communities.
If you do exert that pressure using gaslighting (‘you have low expectations’), many amazing and hard working staff will leave our wonderful profession or such schools and seek a fairer contractual relationship.