When he speaks to the Florida Board of Education on Wednesday, Escambia County schools superintendent Malcolm Thomas has a stark message: The state's teacher shortage is not improving."Teacher recruitment and retention is a major concern for superintendents," Thomas writes in his prepared comments, which appear on the board agenda. "There are just not enough teachers on the bench, and the bench is not deep. Enrollment in colleges of education is down. Superintendents have to use substitutes to fill the gaps. Ultimately, the education of our students will suffer. We must work together to address this critical teacher shortage."Some subject areas fare worse than others, according to the Department of Education's metric for determining the biggest areas of need.In advance of the 2019-20 hiring season, the department has presented its updated list of the most critical shortage areas. For the third year in the past four, general science tops the chart, even as schools endeavor to emphasize science and math.Math teachers are third on the critical shortage list behind English teachers, which topped the list in 2017-18.2019-20 Teacher Critical Shortage Areas [Florida Department of Education]General science teachers comprise just 1.5 percent of certified educators statewide. In 2017-18, 2.8 percent of all general science courses were taught by teachers not certified in the field.This year, the state projects just under 5 percent of general science teaching spots to be vacant.State law calls for differentiated pay rates for teaching positions on the state's annual critical shortage list.