DETROIT -- The company that manages one of three Detroit charter schools that may form a union has told teachers at the school they're walking away from the school they founded.

In a statement released Friday, Progress Michigan, a liberal advocacy group, announced New Urban Learning will end its relationship with University Yes Academy. Teachers at University Yes Academy will be voting on whether to unionize on May 6.

"I was shocked when they told us they were leaving, and couldn't believe that they would walk away from the school," said Rebecca Kissel, a 6th grade teacher at UYA, in a statement. "Their choice to leave will impact our families, and as far as I know there is no transition plan for next year. This just feels like another attempt to stop us from organizing."

According to Progress Michigan, this isn't the first time New Urban Learning has shown unfair labor practices.

The National Labor Relations Board cited New Urban Learning for violating labor laws earlier this year, including retaliating against teachers who attempted to unionize.

The future of the school will be discussed at a school board meeting at noon Tuesday, but some teachers are concerned because they will be teaching and unable to attend.

"It is extremely frustrating that we can't attend a meeting that will impact the future of our school," said Debra Chen, a 7th grade teacher. "We delivered a request to change the meeting that was signed by a majority of our staff to Bishop Edgar Vann, the Board Chair, and he flat out told us no."

On Wednesday, it was announced teachers at University Yes, University Prep and University Prep Science & Math filed petitions to be represented by Michigan Alliance of Charter Teachers and Staff, or ACTS. Michigan ACTS is an affiliate of American Federation of Teachers of Michigan.

It's rare for charter schools in the state to unionize. There are only six total unionized charter schools in the state out of 306. In Metro Detroit, there are three charter schools that are unionized: The Arts Academy in the Woods, Cesar Chavez Academy and James and Grace Lee Boggs School.

AFT of Michigan represents about 200 charter school teachers.

If University Yes, University Prep and University Prep Science & Math all decide to unionize, they will more than double the number of charter teachers in the union. About 250 teachers would become a part of the union if unionization is approved.

In order to hold such an election, at least 30 percent of teachers must have already supported joining a union.

Teachers from University Prep and University Prep Science & Math filed a petition requesting an election with the National Labor Relations Board on Tuesday, according to Progress Michigan.

A message was left with New Urban Learning seeking comment for this story Friday afternoon.

Kyle Feldscher is the Capitol education and MSU reporter for MLive Media Group. Reach him via email at kylefeldscher@mlive.com or follow him on Twitter at @Kyle_Feldscher. Read more stories here.