The Education Ministry is planning to investigate how the math grades issued by high schools affect the final grades that appear on students' matriculation certificates, amid concerns about uneven grade inflation.

Currently, a high-schooler's final grade in a given subject is the average of the school grade and the student's matriculation exam score. The final grade counts toward the matriculation certificate.

A reevaluation is necessary because matriculation scores and final grades differ by more than 10 points in some cases, Education Ministry sources said. This raises questions about the validity of the schools' grades, and calls to attention the fact that there are no clear rules or unified policy on the matter.

"We cannot have two students receive an identical matriculation score but wind up with two very different grades because one had a nicer teacher and one had a strict one," said an Education Ministry source.

The mathematics matriculation exam is being held today. Schools have ordered 310,515 exams of differing degrees of difficulty.

A ministry review found that the average school grade in math was 10 points higher than the average matriculation score last year.

The gap was apparently even higher in previous years.

"We could ask why there is such a gap between the two grades, since the school grade is supposed to reflect the student's achievements and abilities," said a ministry source. "Universities have been warning us for some time that schools inflate students' grades, and this undermines the credibility of matriculation certificates."

"Teachers are using the grades to reward or punish students. There are big differences between schools when it comes to grades. Some schools bloat math grades and give students points they don't deserve. The problem is not the gap between the two kinds of grades, because everyone benefits from this, but the discrimination faced by students who have stricter teachers, or maybe a teacher who simply did not like them," the ministry source said.

Generally, the school grade and the matriculation score are each worth 50 percent of the final grade. However, when the gap between them is great - when the school grade is at least 20 points higher than the matriculation score, or the matriculation score is at least 12 points higher than the school grade - the two factors are weighted differently.

A review two years ago found that dozens of schools had generous grading policies. A handful were found to be particularly strict.

The need to investigate grading policies was most recently discussed on the Mathematics Association web site, where commentators offered a new formula to calculate the two grades. The formula enables schools to categorize students in such a way that does not harm their average grade, but also does not give them an advantage over students at other schools.

The Association's head, Hebrew University Professor Azriel Levy, argued in an article that "a school that grades strictly will have an average final grade of 70 points."

He added, "By granting high grades, the school may raise its students' average final grade to as much as 80 points."

Oren Yahalom, a Tel Aviv 12th-grader said the school grades were a form of protection. "The school grades are there to protect the students, and therefore it's not a problem that they are higher than matriculation scores." There is a lot of pressure ahead of the mathematics matriculation exam, and therefore the high school final exams are like a 'safety net' for us," he said.

The mathematics matriculation exam is scheduled to begin today at 1 P.M. The last test begins at 6 P.M. and ends 75 minutes later.

Two years ago, the average mathematics matriculation exam score was 78.1 percent for those who took three units of the subject, on a difficulty scale of up to five. For four units, it was 79.1 percent, and for five units, it was 85.4 percent. Of the total, 52.6 percent of students took the three-unit exam.

The Education Ministry said its data shows that girls do better than boys on the exams.