Social media are becoming a critical part of communication in everyday lives and are a common form of communication for many students in and outside of school. Accordingly, English learner (EL) students are using social media-based communication to gather information, maintain friendships, and express multiple identities. Considering that social media have been a driving factor in students' literacy practices, it is critical that teachers incorporate this type of social writing into their curriculum and instruction to engage students and to better support their language and literacy learning and development. Research has shown that social media involve changes in modes, authorship, styles, genres, social relationships, and time and space of literacy practices (Elola & Oskoz, 2017; Lam, 2013; Shin, 2014; Toohey et al., 2015). This kind of textual practice has been shown to support second language (L2) development, giving expression to a wider variety of rhetorical goals and expanding audiences (Gee & Hayes, 2011). However, while most of these studies have examined L2 learners' out-of-school literacy practices, there are few studies about multilingual learners'/L2 learners' uses of social media in school settings. This study explores how a sixth-grade teacher used social media in her English and Language Arts (ELA) lessons in a U.S. elementary classroom. Specifically, it examines the kinds of affordances available in social media-based writing, and how students process those affordances in writing genre texts.