The Swedish national syllabus for English recommends that upper secondary English education promote competence in international communication (Skolverket, 2022). As pronunciation differences may be the major cause of misunderstandings in international communication (Deterding 2013), listening skills and positive attitudes related to diverse accents need to be part of English education (Forsberg et al. 2019; Jeong et al. 2021). However, there is a lack of research-based teaching methods and tools, reflecting the longstanding monolingual bias in the study of second language acquisition (Ortega 2014). We therefore investigate the effects of an intervention conducted over three weeks in an upper-secondary class (N=32) and using six listening activities designed based on contact theory (Allport 1954; Pettigrew & Tropp 2006) and the principles of high-variability perceptual training (Lindemann et al. 2016). Pre- and post-tests measuring the intervention’s effect on listening comprehension and attitudes towards unfamiliar accents will be compared with a similar class as a control (N=32). In addition, a focus group of pupils from the intervention group will share their experience of the activities and potentially demonstrate effects not measured by the quantitative data. The findings will provide evidence regarding the effectiveness of this contact- and perceptual-training approach with English learners, informing the development of global Englishes teaching and challenging the monolingual bias in research on second language acquisition.