Student performance in Mexico is assessed by a wide range of instruments, ranging from national standardised assessments to continuous formative assessment in the classroom. All students are assessed in an on-going manner throughout the school year in each curriculum area or subject. Marks used to report student achievement are on a scale of 5 to 10. Assessment criteria and methods are defined by each teacher. There are also externally-based national final examinations at the end of both primary (Instrument for Testing New Lower Secondary School Students, IDANIS) and lower secondary education (National Upper Secondary Education Entrance Exam, EXANI I). These assessments serve diagnostic and selection (by school at the next level) functions. At the national level, there is also a full-cohort external assessment (National Assessment of Academic Achievement in Schools, ENLACE) which is used for diagnostic and improvement purposes but which has “high stakes” for teachers and schools. In basic education, ENLACE is administered annually to all students in third to ninth grades in Spanish and mathematics and a third subject which varies every year. A major asset is that assessment is seen as part of the professional role of teachers in Mexico. Other strengths include the introduction of a new comprehensive framework for classroom-based assessment; the progress made in aligning marks with expected learning outcomes; the good attention to reducing grade repetition; the promotion of the involvement of parents in their children’s learning; and the capacity for implementing large-scale assessments. However, considerable challenges exist in building effective student assessment approaches. These include the currently traditional approaches to teaching and assessment; the prevalence of teaching to the test across the school system; the excessive reliance on multiple-choice tests; the great number of objectives for ENLACE; marking practices with little pedagogical significance; the lack of consistency of student assessment across schools and classes; the limited capacities at the state and local levels to support classroom-based assessment; and the need to improve instruments for reporting marks.