Go to the 'char_create_combinations', there is a column called 'expansions_req', you can set this to a really high number as to allow no access to said races. A query below to update them all beyond player reach.
Code:
/*Restricting Iksar, Vah Shir, Froglok, and Drakkin.*/
UPDATE char_create_combinations SET expansions_req = 999999 WHERE race = 128;
UPDATE char_create_combinations SET expansions_req = 999999 WHERE race = 130;
UPDATE char_create_combinations SET expansions_req = 999999 WHERE race = 330;
UPDATE char_create_combinations SET expansions_req = 999999 WHERE race = 522;
NOTE: 999,999 Is not a real expansion, this is just a number beyond current expansion that keeps players from accessing a certain race or class.