All positions in the bureau of police, except as hereinafter provided, in cities of the second class, shall be in the competitive class of the civil service of such cities. This act shall not apply to or include superintendents of police under the direction of the department of public safety by whatever title his position may be designated, nor his ranking assistant superintendent by whatever title his position may be designated, nor to the inspectors or chief clerks in bureaus of police in such cities, nor to school guards.
53 P.S. § 23531