The study measured 15-year-olds' teamwork, interactive, and problem solving skills.

According to the Ministry of Research and Education, the study included about half of all 15-year-olds in Estonia in 2015, some 5,587 students. The published results now have Estonia at 535 points, which is the best result across all of the European countries included in the study.

The study examined the problem solving skills of 15-year-olds working in teams, defined as students' ability to participate in a process in the course of which at least two team members try to solve a problem together. The effort and understanding for each other the team members display as well as the pooling of their knowledge and skills in an exercise is what makes up the eventual score.

In the study's global ranking, Estonia shares the fifth and sixth ranks with Canada. Ahead are Singapore (561 points), Japan (552 points), Hong Kong (541 points), and South Korea (538 points). Compared to the other countries in the OECD (Organization for Economic Cooperation and Development), Estonia is ahead of the average.

The Estonian students of this age group stand out for their ability to take others into account when working together. Among other things, those students who score better results in tests are better integrated and get along with others. This includes fewer complaints about bullying and being treated unfairly by the teacher, a sense that they are supported, and they talk to their parents more after school, according to the accompanying report of the ministry.

The problem solving skills of those 15-year-olds the study found don't feel that teachers treated them unfairly are better as well. Students who frequently use IT gadgets in school as well as those who participate in sports before or after school do less well in terms of problem solving skills, the study showed.

While the results of Estonian 15-year-olds depend less on their socioeconomic background compared

The socioeconomic background of 15-year-olds in Estonia still plays a role, though a smaller one compared to the OECD average. At the same time, gender as well as the language of instruction play a bigger role than elsewhere: There is a 26-point gap between female and male students of the age group, with the former in the lead.

The study also measured a similar gap in reading skills, where the girls did 27 points better than the boys. Male students in the study were slightly ahead in sciences (by three points) and mathematics (by seven points).

The study describes a 49-point difference between Russian speakers and Estonian speakers in the problem solving skills category.

Russian-speaking students scored fewer points across the board, also in sciences (44 points behind), reading skills (36 points behind), and mathematics (32 points behind).

The ministry's comment on this result is that it shows that Russian-language schools still need additional support to reduce students' dependence on the school's language of instruction.

In its report accompanying the study, the Ministry of Education and Research writes that "a possible reason" for Estonia's performance in the latest PISA study could be the autonomy schools are granted here.

According to the ministry, this means that though the state curriculum dictates the results a student needs to achieve to progress through the Estonian education system, the approaches to achieve the results are in the competence of the schools and teachers.

This autonomy can be seen in the great variety of results as well, which differ greatly from school to school. In the category that measured teams' problem-solving skills, the lowest number of points scored was 378, while the highest-scoring school made it to 658.

The study examines the skills and knowledge of 15-year-olds in functional reading, mathematics, and the sciences. The study is carried out every three years in all three areas.

Estonia participated for the fourth time in 2015. The first time Estonia was included in the PISA study was in 2006, when it looked mainly into students' performance in the sciences. In 2009 the focus was on functional reading, in 2012 on mathematics, individual problem-solving skills, IT, reading and maths, and economics.

The 2015 study included 72 countries, 51 of which carried out teamwork skills studies. In Estonia, 78 percent of test-takers were Estonian speakers and 22 percent Russian speakers.