Ken Livingstone was among the speakers at what is thought to be the largest fundraising event staged by the Stamford Hill community.
Seven-hundred guests at a central London dinner raised £500,000-plus for the Side by Side integrated nursery and special needs school.
The school is operating from temporary premises in Stamford Hill as it seeks funding to secure its long-term future in a permanent home.
Addressing guests at the Hilton Metropole in Edgware Road, Mr Livingstone recalled being taken around Side by Side during his time as London Mayor.
"What remained fixed in my mind was the relationship between the children within the school and the teachers and the parents and the community," he remarked.
"I know that my successor as mayor [Boris Johnson] has looked equally sympathetically on this school and I'm not at all surprised about that.
"Some things are just completely above party politics and elections and Side by Side is one of those things."
Side by Side chair Yossel Margulies was "absolutely overwhelmed by the unprecedented support that the Jewish community has shown for the beautiful children.
"This fantastic event has been a tribute to them and no more than they deserve."