Chicago teachers were to begin a fourth day of their strike Thursday as school officials offered a concession on tough teacher evaluations, a key strike issue. But the Rev. Jesse Jackson, who has a track record of solving sticky situations, said he was disappointed at the lack of urgency in negotiations. \"The sense of urgency within the room does not comply with the sense of urgency in the streets,\" said Jackson, who met separately with union President Karen Lewis and school board negotiators, volunteering to help mediate. \"They should be meeting around the clock,\" he said. \"With each passing day, the pain is compounded.\" \"Both sides have dug in,\" he told reporters. \"At some point, they can\'t hear each other.\" The district proposal softens an evaluation system demanded by Mayor Rahm Emanuel that the union said could put nearly 30 percent of public school teachers on the path to dismissal if they didn\'t improve their performance within a year, the Chicago Sun-Times said. Emanuel has called for teacher performance to be evaluated in part on the results of student standardized tests. The union says the tests don\'t take into account socioeconomic differences among students in vastly different neighborhoods. Another key issue involved rehiring teachers laid off from schools that get shut down or shaken up. The proposal made public Wednesday would let teachers vulnerable to dismissal stay at their jobs indefinitely, provided the test scores didn\'t dramatically decline after the first poor score. \"I think it\'s a pretty generous concession,\" Tim Daly, president of New York\'s New Teacher Project, told the Sun-Times. The project seeks to ensure poor and minority students get equal access to effective teachers. Union officials gave no indication Wednesday if the proposal was a significant step forward, saying only small progress was made in talks. Rallies by striking teachers were smaller in number Wednesday than on the strike\'s first two days. At a rally union organizer John Kugler asked the crowd of red-shirted teachers if everyone was doing OK on a personal level. \"I need money!\" a teacher yelled out. Other teachers laughed, the Chicago Tribune said. The district is the third largest in the United States, with about 350,000 students normally attending more than 600 schools. The strike is Chicago\'s first in 25 years and the first in a major city in a half-dozen years. Chicago\'s longest teachers strike went on for 19 days in 1987. The longest strike in the United States was in New York City in 1968. That strike dragged on from May to November, shutting down public schools for a total of 36 days.