The bonds shall be legal investment: for all trust funds; the funds of all insurance companies, banks, and trust companies; the state school funds, and for all sinking funds under the control of the State Treasurer; and whenever any moneys may by law now or hereafter enacted be invested in or loaned upon the security of bonds of states, counties or school districts in the State, such moneys may be invested or loaned on the security of the bonds of such district.