simulation that encompasses all levels of basic education, since the LAYS is designed to capture the education life of students from 4 to 17 years of age. Two, it has the largest country coverage, with 157 countries and 97% of the world’s population aged 4–17. And three, it combines access (including dropout rates) with quality.

The second simulation exercise focuses exclusively on the expected learning losses at early secondary, as measured by PISA and defined in terms of an average PISA score. The third, and last, simulation translates the impact of a PISA mean score shock into the share of children performing below the minimum proficiency level, as defined by OECD and UIS in the context of the SDG 4.1.1c.<sup>48</sup> One important element in these simulations is the possibility to present results in monetary terms. In order to do that we use expected earnings information from ILO (2020) and World Bank (2020c), and the expected long run return to education. We also compute aggregate results by bringing all expected earnings losses to their present value, assuming a work life of a 45 years and a 3% discount rate. In order to make these results more realistic, we also adjust the aggregate loss by the expected adult survival rate (following the World Bank HCI), and the fact that not all workers will always be in gainful employment (following the measure of Human Capital Utilization described in Pennings, 2019).

We propose three global scenarios for the construction of our lobal simulation (Table 1). In the optimistic scenario, we assume that the length of school closures _(s)_ , as defined above, is an average of 3 months. In the intermediate scenario, we expect schools to be closed for 5 months. In the last, and most pessimistic scenario, we expect schools to be closed for 7 months, or 70% of the school year.

These scenarios are aligned with what we have been observing with the existing data on school closures from both UNESCO and the World Bank. As of June 8<sup>h</sup> , school systems were closed on average 79 days, or 2.6 months<sup>49</sup> (Figure 3). If we include in this school closure estimate the announcement of several countries that they will only reopen their schools by August or September, the average expected school closure will increase to 110 days, or 3.6 months, and those are mostly northern hemisphere countries (Figure 4).<sup>50</sup> In the optimistic scenario, we are not assuming that schools might close again, nor that the summer learnings loss will be significantly larger than usual. Our intermediate scenario, with an average 5 months of school closure, and our pessimistic scenario with 7 months of school closure extends the length of the expected school closure.

> 48 PISA defines minimum reading proficiency as a score below level 2 which is 407.47 points.

> 49 School closure days were only counted until June 8th, 2020, using the UNESCO school closure monitoring database, available at https://en.unesco.org/sites/default/files/covid_impact_education.csv (as of June 8th 2020). 50 3.6 months of school closures includes a subset of 62 economies which have already reopened their schools, or announced a date in which their educational system will be re-open; the 2.6 months average school closures is the measure of actual number of days systems have been closed until June 8<sup>th</sup> , 2020. In this later case, the 150 economies in which schools are still closed, were censored at June 8<sup>th</sup> .

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