Competing interests
PB is the Executive Chair of EI; IF is a paid employee of EI but has no competing interests. DE and CF received research grants funding from EI but have no competing interests. SKe, NM and SiS are employed in these research grants but have no competing interests. SKa and HR receive research funding from EI but have no competing interests. RB, DS, and SSh declare a potential competing interest due to the involvement of Pratham Education Foundation (an independent organisation), which currently works to improve the quality of education in India. AE has no competing interests.