The Chicago Teachers Union called on the school district Wednesday to delay the reopening of high schools targeted for April 19 by at least a week so scheduling and vaccination issues can be resolved and officials can better understand the current rise of COVID-19 cases and variants.

School district officials responded that they still plan to have students return on April 19, the start of the last quarter of the school year. They said they will continue to keep families updated as talks progress. About 26,000 high school students — 37% of the total population, excluding charter schools — have opted for in-person learning. (Each charter school network has a different reopening plan).

“It is disheartening to see yet again that CTU is choosing to create uncertainty for families and their own members when they know and privately agree that our high schools are safe and prepared to open,” CPS officials said in a statement. Mayor Lori Lightfoot on Wednesday also said it was her expectation that high schools would open as planned.

In a Zoom press conference Wednesday morning, CTU President Jesse Sharkey said the school district can reopen without an agreement with the union, but warned that it won’t go well if teachers and staff are not onboard. He said high school staff could refuse to go in, as elementary and preschools teachers threatened in January and February. Staff are expected back on Monday, April 12.

“I was hoping not to be back here since we were just here a couple months ago,” he said.

Just last week, Governor JB Pritzker signed a bill that broadens the issues the union can bargain over to include safety. The union’s general counsel said the school district is now compelled to “collaborate and cooperate” with the union.

CTU argues that Chicago appears to be on the brink of a district-wide return to remote learning. On the call, Sharkey pointed to troubling COVID-19 trends: The city’s positivity rate has climbed to 5.2%, and city officials have said that new cases are concentrated among young people. He also noted that as of Wednesday Chicago has met two of three criteria that would trigger a rollback. These are an increase in the positivity rate for seven days in a row and the rate being 15% higher than the week before. The final metric is a positivity rate above 10%.

Sharkey said the school district should immediately start vaccinating students 16 and older. That’s the youngest age that students are eligible. The school district said it is developing a plan with the Chicago Department of Public Health to get students vaccinated, noting that starting Monday they can go to vaccination sites that are not operated by the city.

Sharkey also said the union and school district disagree over student schedules. He said union officials thought most students would be in school only two days a week to reduce their potential for exposure, but recently the school district said as many as 70% would be invited back four days a week. CPS has previously said it would offer four days a week at schools where a smaller number of students are returning.

School district officials said they have presented the union with a set of comprehensive proposals and received counter proposals from the CTU last night.

CPS officials also note that all staff have now had an opportunity to be vaccinated, either through CPS’ program or other avenues. In negotiations over the reopening for elementary students, the union pushed to delay in-person learning until staff could be vaccinated, a demand that the school district rejected.

But, much to the frustration of CPS officials, the school district can’t say definitively how many staff have been vaccinated. In a statement, school officials blamed the union for the district’s lack of data, saying “due to directives from CTU leadership which discouraged reporting, staff reporting is incomplete.”

At the CTU press conference Wednesday, teachers said they are also frustrated that requests by staff to continue working from home have not been answered. Though many staff have been vaccinated, some are still awaiting second shots. Also, some staff are concerned about going into schools if they live with family members who are medically compromised or who have not been vaccinated. Some parents are particularly concerned about exposing their children to COVID-19 before they are vaccinated.

The negotiations over high school reopening have been going on since the beginning of March, and the two sides have been meeting several times a week.

In the midst of negotiations, the school district is trying to keep parents informed. In addition to sending letters to parents, the school district held a citywide high school town hall and schools are holding meetings this week.

But some parents said the lack of information around high school reopening is frustrating. One group of pro-reopening parents is calling on Pritzker to demand all schools offer in-person learning.

Jordan Sadler, whose son attends Amundsen High School on the North Side, said she told the school district that her son will return in order to preserve that option. The school district will let students go from in-person learning back to remote learning, but once they choose all remote, they can not change their mind.

Sadler said she is still waiting to see what her son’s schedule will be and wants to be sure that he is not putting other teachers and students at risk. Her son has received his first dose of the vaccine.

“I have a whole host of questions,” she said. “I am really waiting to get information so we can decide if that is going to be a situation that makes sense.”

The teachers union was able to secure the right to bargain the reopening of high schools in its agreement over the resumption of in-person learning for preschool and elementary school students. But, after the bitter fight over that deal, the union and the school district said they did not think high school would be as contentious.

The union, as is often the case, has teachers and other staff at the table. The school district has countered with a team of principals.

Sarah Karp covers education for WBEZ. Follow her on Twitter at @WBEZeducation and @sskedreporter.