PORTLAND, Maine — The man who founded the Baxter Academy for Technology and Science, a charter high school expected to open in Portland in September, has been forced out of his post as executive director, the school’s board announced Thursday.

Baxter’s board of directors dismissed John Jaques from his post due to financial mismanagement, Allison Crean Davis, the board’s vice chair, wrote in a memo released to news media.

“Last month, it came to the board’s attention that the finances proposed within Baxter Academy’s budget were never put into place,” Davis wrote. “Without the proper financing, the school did not meet one of the key requirements necessary to sign our charter contract and open our doors to students in the fall. This discovery was a catalyst for reckoning with what we have deemed a pattern of mismanagement.”

The Baxter Academy gained approval from the Maine Charter School Commission in July 2012 on the condition it open in September 2013. The school is now set to open Sept. 3, Davis said, and it has letters of intent from 158 students from throughout southern Maine with more on a waiting list.

Charter schools are public schools of choice that operate independently of local school districts. Maine became the 41st state to allow charter schools following a law that passed the Republican-controlled 125th Legislature in 2011.

Maine currently has two charter schools open and operating, which enroll 106 students. In addition to Baxter, the charter school commission has signed off on two other charter schools that have yet to open.

Baxter’s curriculum will focus on the STEM disciplines of science, technology, engineering and math.

Jaques responded late Thursday that he was “disappointed” by the board’s choice to dismiss him and said the board removed him at the request of a potential donor who promised the school $250,000.

“I believe that the board of directors has acted inappropriately and unethically,” he said in a statement.

Davis said in her memo that Baxter Academy is “in a stronger financial position than ever before” and that the board is interviewing candidates for the executive director’s job.

“The board made a decision that it would support a large donor, who promised a lot of money if they would get rid of me,” Jaques said in his statement. “It feels like the board has sold me and the school’s students out.”

He disputed the allegations of mismanagement.

“There was no mismanagement,” Jaques said. “We’ve been working for two weeks to reach an amicable agreement, but I guess at the end of the day, their loyalty was to the promise of money.”