The survey is administered in lower secondary schools (ISCED 2) and, as an option, is administered in primary (ISCED 1) and upper secondary (ISCED 3) schools. The survey is also optionally administered in PISA sampled schools, forming a TALIS-PISA link. Therefore, this TALIS 2018 conceptual framework builds on the previous two cycles in 2008 and 2013 and underpins the survey’s focus on effective instructional and institutional conditions that enhance student learning, while describing how these vary both within and across countries, and over time.