The president of the state’s largest teacher’s union says students are starting this school year in the midst of a critical teacher shortage.Jolene Franken leads the Iowa State Education Association. She says math, science, special education and guidance positions are in short supply. She says schools are going to great lengths to find teachers for some subjects.Franken blames low salaries for the lack of interest in teaching. She says Iowa is ranked 35th in average teacher salary and is five thousand dollars below the national average.She says the competition for people to fill teaching jobs is tougher than ever as all types of businesses are offering better pay than schools.Both political parties are making teacher pay an issue in the fall campaign.Governor Vilsack will hold a 10:30 a.m. news conference tomorrow to release teacher pay recommendations devised by a panel of educators and business leaders.