Approximately 30% of students in Australian schools are from language backgrounds other than English (LBOTE). Some LBOTE students speak English as their first language and do not require English language support, while others (about 25% of the student population) are learning English as an additional language or dialect (EAL/D). These students face the challenging task of learning English while, at the same time, learning the curriculum through English. As such, EAL/D students need 'targeted, systematic and explicit instruction based on their language needs and prior learning' (Australian Curriculum, Assessment and Reporting Authority [ACARA], n.d.-a). English language proficiency is important for participating in all parts of curriculum learning. Without appropriate instruction and support, EAL/D students are at risk of academic underachievement and plateaus in their English language and literacy skills (Australian Council of TESOL Associations [ACTA], 2022). Historically, there has been limited evidence regarding the length of time required for EAL/D students in Australian schools to develop the level of English necessary to participate in curriculum learning. While considerable research into how long it takes students to learn English has been undertaken overseas over the past 40 years, little research has been conducted in Australia. The aim of this project, therefore, was to contribute evidence of how long it takes Australian students to develop the level of English required for participation in curriculum learning. This aim included describing students' progress through the phases of English language development outlined in the EAL/D Learning Progression: Foundation to Year 10 (ACARA, 2015). Research into how long it takes to learn English is methodologically complex. Achieving the project's aim was made possible by longitudinal and comprehensive data provided by the NSW Department of Education (DoE) -- Australia's most populous education system (Australian Bureau of Statistics, 2023) and one with a high proportion of LBOTE students (39.3% in 2024 [NSW DoE, 2024]). The data provided by NSW DoE included NAPLAN results from students in New South Wales public schools from 2014 to 2022 and NSW DoE's EAL/D Annual Survey over the same period. Over 110,000 English as an additional language (EAL) students in New South Wales public schools across primary and secondary years who met the project inclusion criteria were included in this research. First Nations students who are learning English as an additional dialect were not included in the research due to uncertainty about the completeness of data for First Nations EAL/D students, the differences in experiences compared to EAL students who migrate to Australia, and principles of Indigenous Data Sovereignty, which indicate that research on First Nations students should be led by First Nations researchers in consultation with First Nations communities.