In very weak schools, the improvement required can be extensive. It takes time to rebuild a school to meet the Ofsted framework. It takes good staff and very committed volunteer governors. ( could you volunteer @Lovelyveg80 )
One of the biggest issues, especially in a school causing concern, is finding staff. Recruitment is difficult generally but to improve a school requires those who can give time to work over and beyond, those who will thrive on scrutiny, those who are not worried about the perception of a school.
Add to that some of our small schools, trying to improve a whole curriculum, every subject, improvement by one full time teacher and one teaching headteacher. Just about impossible!
Often schools in our most vulnerable, highly disadvantaged communities are those that require improvement. Staff need to be highly skilled in more than just the academic. Mental health, emotional health, etc.