All moneys of a district, from whatever source derived, shall be deposited in one or more banks or trust companies, and, if the district shall so require, each of such accounts shall be continuously secured by a pledge of direct obligations of the United States of America or of the State of Mississippi having an aggregate market value, exclusive of accrued interest, at all times at least equal to the balance on deposit in such account or accounts. Such securities shall either be deposited with the district or held by a trustee or agent satisfactory to the district. In lieu of any such pledge of such securities, said deposits may be secured by a surety bond or bonds which shall be in form, sufficiency and substance satisfactory to the district.