“…The critical factors of HL learning and development often include age of immigration or age of onset of bilingualism, parental education, SES, and birth order (e.g., Ahn et al, 2017;Armon-Lotem et al, 2015;Kim & Pyun, 2015;Montrul, 2008), parents' attitudes and home environment (e.g., Kang, 2015;Park & Sarkar, 2007), community engagement (e.g., Leeman et al, 2011), ethnic and cultural identity (e.g., Lee, 2002), school ideologies and teachers' attitudes (e.g., Seals, 2018;Yilmaz, 2016), and societal accessibility to HL learning (e.g., Becker, 2013). However, debates on the critical factors are ongoing due to the varying contexts, dynamics among factors, and methodological issues (Duff, 2019;Flores et al, 2020;Ortega, 2020).…”