AUGUSTA — At least five groups are applying to open charter schools in Maine this fall.

State education officials had anticipated letters from four groups, proposing a statewide virtual charter school, a primary school in Cornville, a high school in Portland and a conversion of the Maine Academy of Natural Sciences in Fairfield to a charter school. They weren’t expecting one that came in from the Piscataquis County town of Monson.

Don Dunfee hopes to start a K-6 school in his town this fall or next. Monson Academy would provide an education that connects students with nature. No one answered calls to the phone number on his letter of intent.

Charter schools are public schools that are freed from many of the requirements for traditional schools.

Potential charter school operators have until the close of business today to file notices of intent to apply.

The letters of intent filed this week provide a short description of each school program and information about each school location and target population.

• The Maine Academy of Natural Sciences on the Good Will-Hinckley campus seeks to convert to a charter school.

After closing its school for at-risk young people in 2010, Good Will-Hinckley opened the Maine Academy of Natural Sciences as an environmental and agricultural magnet school for about 20 day and residential students.

The school’s letter of intent projects enrollment for next year at 42, with an eventual goal of 150 students.

• The Maine Virtual Academy is an online K-12 school. The applicant is Maine Learning Innovations, a nonprofit group.

According to the letter of intent, Maine Learning Innovations would contract with K12 Virtual Schools for “curriculum, teaching and school management services.” K12, a for-profit company, is the largest U.S. provider of proprietary curriculum and online education programs.

• Baxter Academies of Maine will apply to open the Baxter Academy for Technology and Science on York Street in Portland. The high school would accept 160 students in the first year and later double to 320.

While Baxter Academy would seek students interested in science, technology, engineering and mathematics, it also would offer “a strong humanities and foreign language curriculum.”

• A group of parents in Cornville is proposing a K-8 community school to replace Cornville Elementary School, which Regional School Unit 54 closed two years ago. Cornville Regional Charter School would group and advance students through the curriculum based on skill level, rather than age.