sentences:  Fifteen- and sixteen-year-old girls compete for the other four scholarships, which are awarded to the top four students in subject-specific Sixth Form entrance exams.For 400 years the best of the Queen's Scholars were elected to closed scholarships at Christ Church, Oxford and Trinity College, Cambridge; since the 1970s, Westminster School boys and girls must win open Oxbridge scholarships by public examination.Prior to 2017, only 40 scholarships were available, and all were awarded to boys sitting the Challenge.