(Chicago News Cooperative) — The Chicago Public Schools are considering an $80 million property-tax increase as they try to close a budget deficit now estimated at $820 million, and they may have to lay off more than 2,000 teachers and increase class sizes without it, according to internal documents obtained by the Chicago News Cooperative. In documents distributed to MayorRichard M. Daley’s office and Mayor-elect Rahm Emanuel’s transition team, the district outlines plans to seek a 2.7 percent tax increase. Without the increase and other measures, class sizes could grow to 36 students, the documents say. The district’s contract with the Chicago Teachers Union currently caps grade school class sizes at 29 students and high school core classes at 28, although space constraints often lead to larger numbers. The district proposal, which sources said had backing from the interim schools chief, Terry Mazany, comes as the district struggles to meet its obligation for a 4 percent wage increase beginning July 1. The increase is required under the Board of Education’s contract with the union.