In order of when they were born:
Gabrielle "Gabby" Marlene Gibson- June 1
Dunstan Jason Diggory- July 26
Leon Brandon "LB" Rivers- November 27
Sheridon Gilbert Doubleday- January 31
Samuel "S" Adam Verona- February 28
Tacita Nicoletta Brown- May 31
Charise Gina Marlow- July 28
Gideon Michael Walker- July 30
Cyrus "Cy" Caleb Cloud- December 31
Mae Marilyn Rivers- January 1
Emily Alberta Desjardin- May 25
Aiden James "AJ" Desjardin- May 25
Tiffani Michelle Royale- August 16
Angela Julie Paxton- September 11
Ophelia Desdemona Foley- October 31
Cassandra Rachel Verona- May 18
Louie Michael Rivers- December 25
Ms. Gibson is in her 30s.
Dunstan is in his early twenties.
LB is 19 (failed a few times).
Mae, Ophelia, Emily, AJ, Angela, and Tiffani are the same age (17, although Ophelia was 16 at the start of the story).
Louie and Cassandra are the same age (16), but Louie was skipped up a grade.
Sheridon, Gideon, S, Charise, Tacita, and Cy are 18.
By astro sign (used the following site for reference, sorry for the mistakes--
www.astrology-online.com/leo.htm:
Gemini (May 22-June 21): Ms. Gibson, Tacita, Emily, AJ
Leo (July 23-August 23): Dunstan, Charise, Gideon, Tiffani
Virgo (August 22-September 22): Angela
Scorpio (October 24-November 22): Ophelia
Sagittarius (November 23-December 21): LB
Capricorn (December 22-January 20): Cy, Mae, Louie
Aquarius (January 21-February 19): Sheridon
Pisces (February 20-March 20): S
Taurus (April 21 - May 21): Cassandra