Although there is no cookie-cut number, the lowest rating for each age group has been moving up a lot. For example, Girls Under 13 used be around 1100, now it's 1361. Much harder to get in.
Here are the lowest rating for each age group (May 2015):
Age 7 and Under: 991 (highest is 1631)
Age 8: 1254 (highest is 2058)
Age 9: 1410 (highest is 2090)
Age 10: 1616 (highest is 2260)
Age 11: 1659 (highest is 2297)
Age 12: 1754 (highest is 2421)
Age 13: 1825 (highest is 2524)
Age 14: 1906 (highest is 2655)
Age 15: 1913 (highest is 2587)
Age 16: 1907 (highest is 2634)
Age 17: 1972 (highest is 2519)
Age 18: 1855 (highest is 2575)
Girls Under 13: 1361 (highest is 2278)
Girls Under 16: 1634 (highest is 2278)
Girls Under 21: 1777 (highest is 2278)
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