How many of those who dropped out or repeated a grade were from rural or low-income families, what had been the findings of the study undertaken by the Algerian Government together with UNICEF in that respect, and what government policies had been implemented since then to reduce the drop-out rate?
在辍学或者留级的儿童中，有多少儿童出身于农村家庭或者低收入家庭？ 阿尔及利亚政府和联合国儿童基金会就此进行的研究取得了哪些成果？