Simon Marks Jewish Primary School in Hackney has drafted in a turnaround specialist to improve its fortunes after a critical inspection last spring.
Gareth Thomas, the new interim head, will outline his plans to parents at special meetings next Monday.
Headteacher Gill Ross, who has been absent since January, has stepped down because of ill-health, governors' chair Howard Pallis said.
The state-aided primary was downgraded from a good school to one requiring improvement after inspectors recorded a decline in teaching quality.
In a newsletter to parents, Mr Thomas said that his background was in "stabilising schools. Previously, I have taken two schools out of special measures and it is my intention to help make this school 'good' again as quickly as possible."
Mr Pallis said the school was "hugely grateful" to Ms Ross for her tireless commitment over the past four-and-a-half years.
The interim head had "a proven track record in focused and rapid improvement of both secular and faith primary schools, regularly delivering upgraded assessments from Ofsted".
And "following a disappointing report from Ofsted and several staff departures - some due to personal and family decisions to move abroad - an almost entirely new teaching team is now in place which is ready, under Gareth Thomas's leadership, to take Simon Marks to the next level".