A school in the polygamous community of Bountiful, B.C., has received top marks in the Fraser Institute's controversial education ratings, despite numerous concerns raised in a high-profile court case examining Canada's polygamy laws.

But a Fraser Institute spokesman readily admits the rankings don't give the whole picture of any school, a point the provincial teachers' union has been arguing for years.

Bountiful Elementary-Secondary School is one of two schools in the fundamentalist Mormon community in southeastern B.C., and both have faced scrutiny at constitutional hearings into the criminal prohibition of multiple marriage.

The case has heard the community's already low enrolment numbers have been declining, especially in higher grades, and few students make it to high school or finish Grade 12.

Bountiful Elementary-Secondary School in particular isn't certified to issue official high school diplomas because of concerns about its curriculum, and the other school, Mormon Hills, was only certified for the first time this year.

But the annual B.C. elementary school ratings from the Fraser Institute, released by the right-wing think tank on Monday, give Bountiful Elementary-Secondary a perfect score of 10/10 -- placing it in a list of the province's No. 1-rated schools.

The rankings are based on scores from standardized tests, which themselves have faced renewed criticism in recent weeks.

The union representing teachers, as well as a provincial association for school principals, have called for the tests to be changed or scrapped altogether.

Peter Cowley, who directs the Fraser Institute's school rankings, said the report card doesn't attempt to address anything other than provincial test score data, which can't account for other concerns raised about Bountiful or any other school.

"We are the first people to say that the report cards don't give the whole picture," Cowley said in an interview Monday.

"It's not just that it doesn't give you the whole picture of Bountiful, it doesn't give you the whole picture of any school. It happens to be the only province-wide testing mechanism that the system has. So why wouldn't you use it?"

Cowley said he's aware of the perennial complaints from teachers that standardized tests don't provide a full picture of how schools or students are performing. But he said those same teachers have also resisted creating better ways to measure success.

He said the teachers union and the Education Ministry could implement additional methods to gauge performance in addition to the tests if they wanted to, but he said teachers are instead focused on getting rid of any standardized measurement.

"The system in general seemingly does not want schools to be compared one with another on virtually any measure. I think that's reprehensible to tell you the truth, but that's the way it is," said Cowley.

"We'd love to see all sorts of other indicators of success, school-by-school, in other areas that are important to parents. They have chosen not to do that."

Susan Lambert of the BC Teachers' Federation, which is an official intervener in the polygamy court case, said Bountiful's rankings only confirm her criticisms of standardized tests and the Fraser Institute's rankings.

"It tells you just how worthless, meaningless and specious the rankings are," said Lambert.

"We've had huge bodies of research which tell us that when you import into a school competitive models, school-versus-school models, what you actually end up doing is depressing achievement scores. It is not a way of encouraging students' achievement."

It's the first year Bountiful's school has made it into the Fraser Institute's ranking, because the organization only includes schools that have 15 student results in each test. In the past, enrolment has been too low to reach that cutoff, explained Cowley.

Bountiful Elementary-Secondary School didn't respond to a call for comment, but posts what it says are its provincial exam results on its website. Those numbers show a gradual improvement during the past five years, with the school beating the provincial average -- in some cases by as much as 30 percentage points -- in almost every category.

B.C.'s education minister, Margaret MacDiarmid, said she was aware staff at Bountiful Elementary-Secondary have been working hard in recent years to improve student performance, and the test scores appear to bear that out. She said she has no reason to doubt the scores accurately reflect the students' performance.

Still, she acknowledged her own government has raised concerns about the quality of education in Bountiful.

"Those skills that are foundational (such as reading, writing and math), they've put in some extra resources, done some extra work and this has been the consequence," MacDiarmid told reporters in Vancouver.

"This is without a doubt a school that stands out in the province, it is a controversial school, but they have done well in the foundational skills and that's all you can take away from this. There are really serious limitations to ranking schools, and we don't actually believe you can rank schools based on how they do on standardized testing."

Despite that caveat, MacDiarmid defended the mandatory tests, which some parents have decided to opt out of after warnings from teachers that the tests are unnecessary and potentially harmful.

"The tests are really important," she said. "If I'm a parent, I want to know how my child is doing."