Proposing a constitutional amendment authorizing the legislature to exempt from ad valorem taxation by a school district a portion of the appraised value of an individual's residence homestead in an amount equal to the lesser of 50 percent of the appraised value of the residence homestead after all other applicable exemptions for which the individual has qualified the homestead are applied or 150 percent of the median appraised value of all single-family residences in the state and authorizing the legislature to exempt from ad valorem taxation by one or more political subdivisions of this state inventory held for sale at retail.