PORTLAND – When a new high school opened six years ago in Poland, it opted for student assessments in place of letter grades and students worked daily with their advisers.

Today, more than 80 percent of the students at Poland Regional High School attend college, and every student is required to apply. By contrast, only 35 percent to 45 percent of the students in the area went on to college before the school opened.

Poland has emerged as a model for a quiet revolution under way in high schools across Maine, where growing numbers of schools are shelving long-standing practices such as grouping students by ability.

Instead, freshmen are being funneled into small groups to work with the same adviser for all four years. Other schools require students take college entrance exams and apply to college regardless of whether they plan to attend.

Machias High School, saddled with mediocre assessment scores and high teacher turnover in the late 1990s, has seen the number of graduates going on to college jump from about 50 percent to nearly 80 percent.

Principal Tim Reynolds said parent involvement has helped fuel a sharp improvement in 11th-grade assessment scores. Machias High scrapped its poorly attended parent-teacher conferences in favor of meetings between students, their parents and the student’s adviser. The students, rather than the teachers, formally present their work to their parents.

“The first year we had 98 percent turnout. Last year we had 100 percent,” said Reynolds.

Houlton High School, where students spend four years in groups with the same advisers, saw 11th-grade assessment scores jump in the past year by encouraging students to take the tests seriously, said Principal Martin Bouchard.

Students took the four-day test in their adviser groups rather than in a large classroom with a teacher they might not know. Students who showed effort were rewarded with special privileges.

Perhaps the boldest new experiment is taking place in Portland, where 86 students are enrolled in the founding class of a new high school that teaches through experience, a concept called expeditionary learning.

“There are going to be tests, obviously, but we actually get to share our opinions,” said Joel Daley, 14, explaining why he decided to attend the new school rather than follow most of his classmates to one of the city’s two traditional high schools.

Maine has been grappling with the failure of its high schools to turn out students prepared to compete in a global economy. While the state’s graduation rate compares favorably with other states, the number of students enrolling in college does not.

A $10 million grant from the Bill and Melinda Gates Foundation three years ago enabled the state to ramp up its high school reform efforts. The Gates foundation is also behind funding the new Portland high school, whose principal, Derek Pierce, is the former principal at the Poland school.