This chapter presents a questionnaire study that asks Swedish upper secondary school students about their informal out-of-school ICT-based literacies and how these feed into their formal school-based writing of English argumentative texts. Two questionnaires in combination with national test grades for an English argumentative text assignment are used to tease apart which out-of-school, ICT-based, and other literacies relate to the grades achieved. This showed that reading in Swedish had a significant impact on the grades achieved when writing in English, but writing in Swedish had a negative impact, with English reading or writing in ICT-based platforms having no impact. However, as the boys achieved as well as girls on the English writing task in the national test, unlike in other subjects, we argue that our ordinal regression analysis failed to capture the impact of informal e-learning of English. Free text questionnaire answers confirmed our view of the important role ICT-based literacies in social media and e-sport have on the informal learning of English and the students’ confidence in writing in English as second language. In sum, e-sports and other out-of-school ICT-based literacies lift boys’ performance in English as second language writing. Finally, this chapter presents some directions for future research.