In all school districts of the second, third, and fourth class, as soon as the school tax is assessed and levied by the board of school directors, the secretary shall compute and enter the same, stating the amount of school tax to be collected on the duplicate herein required to be furnished to the district. A certified copy of such duplicate shall be furnished by the board of school directors to the tax collector in each district. In any school district where the collector of school taxes is also the collector of county taxes the secretary of the board of school directors may compute and add the amount of the school taxes to the duplicate furnished by the county commissioners to such tax collector for county purposes. In all school districts of the second, third, or fourth class, all tax duplicates shall be furnished, as herein provided, to the tax collectors on or before the first day of July in each year.