Section 13.

All the net earnings accruing to the State Permanent School Fund shall annually be added thereto until it has reached the sum of Five Hundred Million Dollars ($500,000,000.00). Thereafter only one twentieth of the annual net earning shall be added to the fund itself, and the remaining nineteenth twentieths shall annually be apportioned to the school districts of the State on the basis of the aggregate actual school attendance in each district during the preceding school or calendar year by persons between the ages of six and eighteen years, and shall be exclusively for educational purposes, subject to such regulations and limitations as may be prescribed by law.