The fund for the support of free public schools, and all money, stock and other property, which may hereafter be appropriated for that purpose, or received into the treasury under the provisions of any law heretofore passed to augment the said fund, shall be securely invested, and remain a perpetual fund; and the income thereof, except so much as it may be judged expedient to apply to an increase of the capital, shall be annually appropriated to the support of free public schools, and for the equal benefit of all the people of the State; and it shall not be competent, except as hereinafter provided, for the Legislature to borrow, appropriate or use the said fund or any part thereof for any other purpose, under any pretense whatever. The bonds of any school district of this State, issued according to law, shall be proper and secure investments for the said fund and, in addition, said fund, including the income therefrom and any other moneys duly appropriated to the support of free public schools may be used in such manner as the Legislature may provide by law to secure the payment of the principal of or interest on bonds or notes issued for school purposes by counties, municipalities or school districts or for the payment or purchase of any such bonds or notes or any claims for interest thereon.