here are some single year age group world records (unofficial--not sure how often this list is updated, though one record is from 2011) for the mile (not 1600):
11 5:07.8 Sydney Tullai USA 1 Feb 99 Downey CA 22 Jan 11
12 4:57.51i Claudia Francis USA 14 Nov 93 New York NY 12 Mar 06
13 4:48.8 Katharina Denz SUI 9 Sep 63 Los Angeles CA 12 Jun 77
14 4:40.1 i Mary Decker USA 4 Aug 58 Richmond VA 16 Mar 73
from the 1500, which is the usual race at the youth level and internationally:
11 4:39.84 Sarah Hopkinson GBR 11 Aug 91 Eton 14 Jun 03
12 4:24.96 Georgie Clarke AUS 17 Jun 84 Melbourne 23 Feb 97
13 4:17.53 Georgie Clarke AUS 17 Jun 84 Brisbane 21 Mar 98
14 4:17.53 Georgie Clarke AUS 17 Jun 84 Brisbane 21 Mar 98
depending on the age of these girls, these could be pretty phenomenal times. don't mean to doubt, but i'm suspicious--are you sure these aren't 1500 marks?