All revenues arising from the taxes hereby levied applicable to the City of Florence in Lauderdale County shall be used exclusively for public school purposes in the City of Florence, including capital outlay, construction, and maintenance of city public schools and the payment of teachers’ salaries and other current school expenses, including the costs of school transportation; subject, however, to all pledges of the revenues from the taxes heretofore or hereafter made to warrants or other obligations of the City Board of Education of the City of Florence.