On the surface, learning a second language may seem to be a simple one- to two-year undertaking. Research shows, however, that it's a far more complex endeavor. This article considers the depth of learning required to become academically proficient in a second language. For instance, language learners learn the basics of reading in a second language within roughly two years, but comprehension may take many more years. Social English develops quickly, but the ability to engage with complex classroom content takes longer. Building vocabulary is key, but it requires robust teaching strategies, i.e., not just having students memorize word lists, but also giving them opportunities to practice structured classroom dialogue and to think about and clarify word meanings (August, Carlo, Dressler, & Snow, 2005). The article also touches upon teachers' misconceptions about second-language learners and the potential impact this may have on their interaction with students. Lastly, it draws attention to the recent call by researchers and practitioners to see language and cultural diversity not as a problem, but as an opportunity to prepare all students for a globally connected world.