§ 2574. Assistant superintendents in a city having a population of one million or more. The title district superintendent used in any law to designate a district superintendent in the employ of the board of education of a city having a population of one million or more is hereby changed to assistant superintendent. The persons affected by this section shall, under such new title, continue to have the pension rights, salary rights, tenure rights, and all other rights they had under the title district superintendent.