These updated Guiding Principles of Language Development and Learning exemplify WIDA’s overarching and ever-present Can Do Philosophy. 1. Multilingual learners' languages and cultures are valuable resources to be leveraged for schooling and classroom life; leveraging these assets and challenging biases help develop multilingual learners' independence and encourage their agency in learning (Little, Dam, & Legenhausen, 2017; Moll, Amanti, Neff, & González, 1992; Nieto & Bode, 2018; Perley, 2011). 2. Multilingual learners' development of multiple languages enhances their knowledge and cultural bases, their intellectual capacities, and their flexibility in language use (Arellano, Liu, Stoker, & Slama, 2018; Escamilla, Hopewell, Butvilofsky, Sparrow, Soltero-González, Ruiz-Figueroa, & Escamilla, 2013; Genesee, n.d.; Potowski, 2007). Multilingual learners refers to all children and youth who are, or have been, consistently exposed to multiple languages. It includes students known as English language learners (ELLs) or dual language learners (DLLs); heritage language learners; and students who speak varieties of English or indigenous languages. 3. Multilingual learners' language development and learning occur over time through meaningful engagement in activities that are valued in their homes, schools and communities (Engeström, 2009; Larsen-Freeman, 2018; van Lier, 2008; Wen, 2008). 4. Multilingual learners' language, social-emotional, and cognitive development are inter- related processes that contribute to their success in school and beyond (Aldana & Mayer, 2014; Barac & Bialystok, 2012; Gandara, 2015; Sánchez-López & Young, 2018). 5. Multilingual learners use and develop language when opportunities for learning take into account their individual experiences, characteristics, abilities, and levels of language proficiency (Gibbons, 2002; Swain, Kinnear, & Steinman, 2015; TESOL International Association, 2018; Vygotsky, 1978). 6. Multilingual learners use and develop language through activities which intentionally integrate multiple modalities, including oral, written, visual, and kinesthetic modes of communication (Choi & Yi, 2015; Jewitt, 2008; van Lier, 2006; Zwiers & Crawford, 2011). 7. Multilingual learners use and develop language to interpret and access information, ideas, and concepts from a variety of sources, including real-life objects, models, representations, and multimodal texts (Ajayl, 2009; Cope & Kalantzis, 2009; Jewitt, 2009; Kervin & Derewianka, 2011). 8. Multilingual learners draw on their metacognitive, metalinguistic, and metacultural awareness to develop effectiveness in language use (Bialystok & Barac, 2012; Casey & Ridgeway-Gillis, 2011; Gottlieb & Castro, 2017; Jung, 2013). 9. Multilingual learners use their full linguistic repertoire, including translanguaging practices, to enrich their language development and learning (García, Johnson, & Seltzer, 2017; Hornberger & Link, 2012; Wei, 2018). 10. Multilingual learners use and develop language to interpret and present different perspectives, build awareness of relationships, and affirm their identities (Cummins, 2001; Esteban-Guitart & Moll, 2014; May, 2013, Nieto, 2010). WIDA is housed within the Wisconsin Center for Education Research at the University of Wisconsin-Madison. © 2019 The Board of Regents of the University of Wisconsin System, on behalf of WIDA