Additional language lessons improve children’s reading skills

By giving school children up to four additional hours of Danish lessons every week for 16 weeks, we improve their reading skills to an extent that amounts to six months of schooling in addition to what other pupils achieve in that period of time.

The article is published in the newspaper Politiken Thursday, April 10


Authors: Simon Calmar Andersen, Louise Voldby Beuchert-Pedersen, Maria Knoth Humlum and Anne Brink Nandrup

Facts: Associate Professor Maria Knoth Humlum, PhD scholar Louise Voldby Beuchert-Pedersen, and PhD scholar Anne Brink Nandrup are affiliated with Department of Economics and Business, Aarhus University. Simon Calmar is professor at the Department of Political Science and Government at Aarhus University. For further information about the study, go to                                       

Today the first results of a major study on mother-tongue based education will be published. The study, which runs over the course of 2013 to 2015, shows a significant improvement of reading skills among some groups of school children and less significant effects among other groups.


The nationwide study is based on 126 fourth grade primary school classes and is divided into two parts. We have examined the effects of two different initiatives that took place over the course of 16 weeks: one group of school children received four additional weekly Danish lessons, and another group of children participated in the new course called General Language Comprehension, which has been developed by a working group appointed by the Danish Ministry of Education. The study is financed by the Ministry of Education, who did not have access to or influence on the analyses and results of the study.


The experiment were conducted as a randomised controlled trial with a comparison group. This means that it was determined by a draw which of the initiatives each school was set to implement. The randomised selection ensures that the schools that implemented additional Danish lessons are no different at the outset from the schools that implemented the new course General Language Comprehension or the schools from the comparison group that did not implement a new initiative. It is therefore safe to conclude that the children’s progress directly results from the implementation of these initiatives.


Effects amount to six months of schooling

The results of the study show that the classes that received additional Danish lessons improved their test results with an average of 0.25 in the national tests on children’s reading skills. But what does that really mean? In order to fully understand the effects of the initiatives, one must bear in mind that the progress that these children experience comes in addition to what they would normally have learned over the course of the 16 weeks following good teaching. We are able to conclude this with great certainty, because a large group of the involved schools functioned as a comparison group, and pupils at these schools received no additional schooling. Supplementary analyses of the national tests suggest that pupils who received regular teaching showed an average improvement of about 0.3 over the course of nine months, which amounts to 0.4 over the course of an entire school year (measured according to the standardised scale that was used for the experiment).


Thus, the average basic effect is 0.4 per year, and the effects of additional Danish and General Language Comprehension lessons come in addition to this. The effects of both initiatives are illustrated in the figure below.

 The effects

Figure. The effects of additional Danish and General Language Comprehension lessons on the pupils’ reading skills, measured through the national tests.


On this foundation we can interpret the results to suggest that the children who received additional Danish lessons or participated in the course on General Language Comprehension for only 16 weeks improved their reading skills with little over 50 per cent compared to the normal progression rate of a pupil over the course of a year. In other words, the progression in reading results amounts to little more than six months of schooling, which comes in addition to the normal progression that an average pupil experiences.


However, the figure also shows great deviation in the effects on the various target groups. The effects of additional Danish lessons are by and large the same for boys and girls. However, the effects on the boys are somewhat more unclear than with the girls. Finally, supplementary analyses show that the initiatives were significantly less effective in children who speak a different language at home, either fully or partly. Among the bilingual pupils, the initiative was less than one-third as effective compared to the monolingual pupils who speak Danish at home. So, while it was possible to determine that additional language lessons lead to progression in the children’s reading skills that amounts to six months of schooling, the effects among the bilingual children amounted to less than two months of schooling.  Actually, the calculations show that the effect of the initiative on the bilingual children was so small that it cannot be ruled out that the additional teaching hours in fact had no effect on the bilingual children’s reading results. Whatever progression there was may be ascribed to other factors.


There is also great deviation in the results from the pupils who did the course on General Language Comprehension. The effects of the initiative on the girls amount to nine months of progress through regular schooling. But the initiative was only one-fifth as effective among the boys compared to the girls. Based on the calculations, we may therefore conclude that the progression among the boys was so small that we cannot be certain that the language course had any real effect on the boys’ reading skills. Similar to the bilingual pupils who received additional Danish lessons, the bilingual pupils who did the course on General Language Comprehension did not benefit very much from the initiative.


It should however be emphasised that the effects have been measured over a relatively short period of time. The long-term effects will be established over the coming years.


Thanks to the schools that actively participated in this randomised controlled trial, we now know with much more certainty than before that additional Danish lessons and the new course on General Language Comprehension have an overall positive effect on the school children. It has also become clear that different groups of pupils benefit differently from these initiatives. Nonetheless, the experiments have provided us with crucial knowledge that we can use in the further work to improve the skills of pupils in the Danish school system as much as possible. 


Simon Calmar Andersen, professor
Phone: + 45 87165725

Maria Knoth Humlum, associate professor
Phone: +45 87165568