CREATE TABLE table_18810 ("Specification" TEXT, "Gender" TEXT, "Junior High School  ( 12\\u201315 yrs ) " TEXT, "Senior High School  ( 15\\u201318 yrs ) " TEXT, "University students and Adults  ( 18yrs+ ) " TEXT)

What is the gender of the junior high school is 24mm?
SELECT "Gender" FROM table_18810 WHERE "Junior High School (12\u201315 yrs)" = '24mm'
SELECT "Gender" FROM "table_18810" WHERE "Junior High School (12\u201315 yrs)" = '24mm'