In England, parents make "choices" (in reality, "preferences") for the state-maintained secondary schools they wish their child to attend. If there are more applicants than places, the school's published admissions criteria are used to give priority to applicants. This article examines how school composition in London varies by first comparing schools that are overtly academically selective with those that are nominally "comprehensive" ("all ability"); second, comparing "comprehensive" schools that control their own admissions with those that do not; third, comparing schools with and without selective admissions criteria; and fourth, comparing schools that use religious criteria with those that do not. We find that school compositions vary. Academically selective schools have fewer students from poor households than comprehensive schools in the same area and have fewer Black and more Indian and Chinese/Other Asian students. Comprehensive schools with autonomy over admissions admit higher attaining students and have fewer students from poor households and with special educational needs, and those with selective admissions criteria admit higher performing children. There are fewer Bangladeshi/Pakistani students and more Black students in schools with a religious character than in those without. Although a range of factors are likely to play a role in explaining the variation in school composition, the evidence suggests that there is "selecting in" and "selecting out" of more desirable students by some schools. Implications for policy are highlighted.