NEW DELHI: Studying mathematics scores of the same set of kids in multiple rounds of tests, a researcher has concluded that kids learn better in their mother-tongue. Kids attending Telugu medium schools - data was gathered in Andhra Pradesh - "on average perform significantly better as compared to English medium students" once factors such as native ability, household characteristics and "parental aspirations" are considered and "controlled for."P Sree Kumar Nair of Division for Child Studies, Centre for Economic and Social Studies and UNICEF, used data collected as part of the Young Lives longitudinal study in Andhra Pradesh and Telangana from 2002 to 2011.His paper investigates the "effects of medium of instruction on learning levels" in general, not just the ability to pick up languages. Mathematics scores from two rounds of tests administered in 2006-07 and 2009-10 to the same batch of 915 children born between January and June 2001 were considered. Though English-medium schools are now preferred and are proliferating, Nair argues that "learning levels of students can suffer at lower levels of schooling" if they have English as medium of instruction. This impacts the poor most as there is rarely any support from the family in learning English or basic concepts in it."I wanted to understand why there are variations (differences) in the achievements of the kids. With a big sample the impact of various factors on learning becomes evidentand clear. Also, Data on the same students in multiple rounds can explain the variations," he says. While the final conclusion is on the medium of instruction, Nair used a wide variety of data covering "child, household, school and community characteristics"gathered by Young Lives through household as well as school surveys. Not all factors are equally significant.The difference in the student-teacher ratios in English and Telugu medium schools is highly significant, with three stars (stars denote level of significance with three as the highest) as is the difference in the proportion of permanent teachers. Telugu-medium school teachers are better paid in both rural and urban areas - as most are in government schools - but there are significant differences in weight, height, wealth and mother's educational levels with rural English medium schools performing better than Telugu ones. As Nair points out in most cases, the English medium schools are private.As more such variables are factored in, the effect of medium of instruction becomes sharper.Nair's analysis shows that "Telugu medium students at primary levels have performed better, as observed after controlling for children's nutritional and time use characteristics.""The step towards transition o the language of instruction and its consequence in terms of perceived economic gains in the labour market is still unclear. Moreover, insistence on instruction in English is certainly a barrier for the poor, rural and lower caste students," writes Nair.