1. I'm looking for a secondary school which has a good music program.
2. My son is at a school which he really likes.
3. Australia is a country where about 30% of children go to private schools.
There are NO objects (of verbs) in your examples.
In ex. 1, "school" is object of the preposition "for", NOT the object of the verb "looking".
In ex. 2, "school" is object of the preposition "at", NOT the verb "is".
In ex. 3, "country" is not an object at all, but subject complement of the subject "Australia".