What total number of the (a) 309 453 children who received foster care grants in the 2020-21 financial year, (b) 154 735 children in the 2019-20 financial year, (c) 386 019 children in the 2018-19 financial year, (d) 416 016 children in the 2017-18 financial year and (e) 440 295 children in the 2016-17 financial year (i) are enrolled in (aa) primary and (bb) high school and (ii) attend school regularly?