Found this study based on Spanish longitudinal via professor Wouter Duyck many of my readers – pun intended – will think it to be relevant.

First of all the study by Jerrim et al shows – again – the link between reading and better academic results:

Consistent with the findings of Jerrim and Moss (2018) the strongest results are obtained for the frequency with which young people read books. In our baseline model specification (M1) regular reading of books is associated with a 0.40 standard deviation increase in age 13–14 reading test scores. Again, the major confounder of this result is that children with higher levels of prior achievement tend to read books more often (as illustrated by Table 2). Once we have accounted for this fact within our analysis, the estimated effect size falls by around one-third, though is still substantial (effect size = 0.28). The inclusion of additional controls for parental reading attitudes and activities and engagement, children’s attitudes towards school and engagement do little to change this result; the effect size in model M5 has barely changed, standing at 0.27. Moreover, although the inclusion of school fixed-effects does lead to some further attenuation of the estimated association (down to 0.22), it remains substantively important in terms of magnitude.

But does it matter what the children read?

Our results provide further evidence that it is not only whether young people read or not that matters – but also what they read. As per some previous research, we find little evidence that reading newspapers, comics and magazines have positive benefits for young people’s academic achievement. The association between the frequency children read these types of text and their scores on a Spanish language test is weak and often statistically insignificant once key potential confounders have been controlled. In contrast, the association between reading books/novels and young people’s academic progress at school is quite strong. Even after a wide range of potential confounders have been controlled (including rich measures of prior achievement, family background, parental reading attitudes and activities, parental engagement towards their child’s education and children’s attitudes and engagement towards school and school fixed-effects) teenagers who read books every or almost every day continue to score around 0.22 standard deviations higher on Spanish Language tests than those who never or almost never read books. Our analysis also provides some evidence of spill-over effects, with frequently reading books (but not other text types) also associated with academic progress in mathematics.

Do note that this study shows again a correlation, not a causal relationship. Another important limitation to take into account is this one:

…our analysis has focused upon academic progress made in reading and mathematics during the early-teenage years. At this point, reading skills are already quite well-developed. Yet we do not currently have evidence as to whether the results we have found hold for children at younger ages as well – such as when children are first starting to independently read. It is plausible that different text types (e.g. comics and magazines) have more positive (or negative) benefits at this point in children’s lives.

Abstract of the study:

It has long been thought that encouraging children to read is likely to be beneficial for the development of their literacy skills. However, a lot less attention has been paid to the issue of whether what students read matters for their academic progress. This paper therefore considers the association between the frequency young people read five different types of text (comics, short stories, books, newspapers and magazines) and their scores on standardised reading and mathematics tests. Drawing upon large longitudinal census data from the largest administrative region in Spain, we find that frequency of reading comics, newspapers and magazines is not associated with the development of children’s cognitive skills. In contrast, there is clear and consistent evidence of a positive and increasing association between the frequency children read books and their academic achievement. We consequently conclude that recommended reading time for children should be focused upon the time they spend reading books and not other material.