The idea that teachers might disproportionately favor better performing and better endowed students is not surprising. This can be linked to two streams of research: (i) curriculum mismatch with student ability; and (ii) stereotype threats. It may be argued that as a part of an efficient strategy, teachers are screening students to identify those that may yield the greatest returns. These teachers dedicate their efforts and time to the students they believe would be most predisposed to learning.

As mentioned in Section 3.2.2, in many contexts, the pace of classroom instruction is determined by the need to cover (often overambitious) curricula rather than student learning (Beatty and Pritchett 2012). This means that teachers often take the least risky route of concentrating on those students who can cope with the curriculum. These typically better‐prepared and better‐resourced students are easier and faster to teach. These are the students who are taught because of the system‐imposed pressures of completing the curriculum—even though they might be aware that a significant share of students are behind the pace of the classroom and cannot follow (Banerji 2000). In fact, in order to ensure that the prescribed curriculum is finished, a teacher might have no choice but to ignore students who are falling behind.

Further, a growing body of literature also demonstrates how teachers tend to favor students of high socioeconomic status over students from disadvantaged backgrounds (for example, in England (Auwarter and Aruguete 2008), in Chile (del Río and Balladares 2010), and in the US (Gershenson, Holt, and Papageorge 2016)). An analysis of 10th‐graders in the US, for example, shows teachers respond to family income when building expectations of student outcomes, and these expectations in turn impact educational attainment (Gershenson, Holt, and Papageorge 2016). The effects of teacher expectations on student outcomes may even start as early as kindergarten (Speybroeck et al. 2012).

Such stereotyping presents a typical example of a mental model (World Bank 2014). By shaping their opinion of a certain socioeconomic class, teachers contribute to a cycle whereby both the teacher and the students themselves underestimate the ability of a poor student (Guyon and Huillery 2014). Teachers might directly or indirectly convey their biased expectations of student ability by modifying how they teach, evaluate, and advise stigmatized students, or those students may modify their own expectations and behavior to conform with teacher bias (Ferguson 2003; Jussim and Harber 2005; Lareau 2011; Lareau and Weininger 2008).

# 4. Caveats

There are two key limitations to this work. We discuss each in turn: _Sampling_ **:** In this work the emphasis was on external validity. To this end, over 16,000 teachers across eight countries and five regions were interviewed. However, to achieve this breadth of coverage, the team had to leverage ongoing data collection. As such, the size of the sample and the precise sampling strategy do not match across all countries. Despite this, the total sample size for each country ranges between 200 teachers in Zanzibar and more than 9,600 teachers in Pakistan. The number of schools visited in each country ranges from 94 in Zanzibar to more than 3,000 in Pakistan (details in Table 1). As such, sample sizes by country are defensible though not nationally representative.

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