Please list the lowest three eligible free rates for students aged 5-17 in continuation schools.
Eligible free rates for students aged 5-17 = `Free Meal Count (Ages 5-17)` / `Enrollment (Ages 5-17)`
SELECT `Free Meal Count (Ages 5-17)` / `Enrollment (Ages 5-17)` FROM frpm WHERE `Educational Option Type` = 'Continuation School' AND `Free Meal Count (Ages 5-17)` / `Enrollment (Ages 5-17)` IS NOT NULL ORDER BY `Free Meal Count (Ages 5-17)` / `Enrollment (Ages 5-17)` ASC LIMIT 3