Japanese elementary and junior high school students are not very good at writing logical essays or explaining how they have solved mathematical problems, a study by the National Institute for Educational Policy Research has found.

The study, covering about 37,000 children in fourth grade in elementary school through students in their final year in junior high, revealed weaknesses in logical and mathematical thinking -- findings also attested to in a 2003 international achievement survey by the Organization for Economic and Cooperation and Development.

The study, the first of its kind by the institute, aims to lead to improvement in teaching methods by examining how thoroughly children have absorbed the education ministry's requirements.

In the essay category, 61 percent of elementary school fourth-graders and 74 percent of third-year junior high students were able to express what they think, but only 32 percent of the younger kids and 69 percent of their older counterparts were able to compose logically organized sentences using paragraphs.

Students also showed poor abilities in creating graphic representations of everyday phenomena, with more than 40 percent of fourth graders unable to illustrate the movement of a swing.

They had difficulties solving a problem in which they were asked to explain how to measure the area of a diagram using figures or formulas, according to the survey.

Based on its findings, the institute has proposed having children keep diaries or observation logs to logically explain why and how they have come to certain conclusions.

In the 2003 OECD worldwide achievement survey, Japanese 15-year-olds ranked sixth in applied skills in math, down from the No. 1 spot in 2000, while placing 14th in reading comprehension, down from eighth.