New Delhi: The CBSE on Tuesday decided not to hold a retest of the leaked Class X mathematics paper even in Delhi and Haryana, saying its survey had found no impact of the leak on students' performance.

"Consequent to the preliminary evaluation of the impact of reportedly leaked CBSE class 10 maths paper & keeping in mind the paramount interest of students, CBSE has decided not to conduct re-examination even in the states of Delhi NCR and Haryana. Hence, no re-exam for class 10," school education secretary Anil Swarup tweeted.

The survey was conducted by evaluating the answer sheets of 1,000 students randomly picked from Delhi, Haryana and Jharkhand who took the test last week and comparing the results with the performance in the mathematics paper last year from the respective regions. (See chart)

It found a dip in the performance this year over last year despite the leak. The dip was sharp in Jharkhand.

A faculty member at IIT Bombay, Prof. Anurag Mehra, who is not connected with the survey, said besides the leak, several other factors such as difficulty level, grading rubric and style and moderation formula could lead to a difference in the performance over the previous year. To extract the impact of a leak, the difference in pass percentages in affected and non-affected areas would have to be compared.

The CBSE has conducted the survey only in Delhi, Haryana and Jharkhand - regions from where the leak has been reported.

To questions from journalists on why a retest was not being held when the exam process had been vitiated, Swarup snapped: "Heavens are not falling if we do not take re-exam of mathematics. But if we take retest, we will cause a lot of inconvenience to lakhs of students."

News of the leak and a proposed retest had brought lakhs of students out on the streets in protest, after which the Centre declared that any re-exam would be held only in the National Capital Region and Haryana, after a survey to assess the impact of the leak.

Swarup added that mere access to a question paper a few hours before the test cannot help much. "It is not so easy to mug up so quickly even if you get a leaked paper," he said.

A notification issued by the CBSE's examination controller K.K. Choudhury on Tuesday said: "Class X examination is essentially a gateway for Class XI, it thus remains largely an internal segment of school education system... Keeping in mind the paramount interest of students, the Board has taken the considered decision to not hold the re-examination of Class X maths paper even in Delhi and Haryana."

The retest of the Class XII economics paper will be held on April 25.