Chicago teachers were due to vote on whether to continue a week-long strike today following a Saturday protest rally that drew thousands.
The city's Teachers Union president Karen Lewis said progress had been made in negotiations over teacher evaluations and she "hoped and prayed" students would be back at school today.
Teachers launched the strike to protect job security, noting that class sizes in state schools were already averaging over 40 in Chicago.
Mayor Rahm Emanuel warned class sizes in state schools could rise to 55, though unions noted that he sends his own children to a private school where classes are capped at 24 students.
The rally targeted the Hyatt Hotel, owned by the Pritzker family, because it recently received millions in property taxes in the form of "tax increment financing" (TIF).
Unions say around $500 million (£310m) is skimmed each year from property taxes meant to fund schools and parks and handed to corporate giants and property developers.
Hyatt's Class Residence chairwoman and billionaire Penny Pritzker holds a seat on Chicago's unelected education board, which recently cut $3.3m (£2m) from five schools leading to 27 teacher redundancies, just as Hyatt was awarded $5.2m (£3.2m) in TIF to build a new hotel.
Ms Pritzker is also President Barack Obama's national finance chairwoman for his re-election campaign.