"Tini returns from school."
Translation:Tini kembali dari sekolah.
Both are correct. Pulang means return home, so "Tini returns home from school" (Tini pulang dari sekolah), whereas kembali just means returns or comes back, so "Tini returns from school" (Tini kembali dari sekolah). She may not have returned home. It could mean she returns to the library or to work or anywhere. Kembali means return but does not specify a place, whereas pulang specifies home. If it were Tini returns home from school, pulang would be more accurate, but in this case where it does not specify, kembali is more accurate:)
1.)Tini kembali "ke" sekolah. Tini returns "to" school.
2.) Tini kembali "dari" sekolah. Tini returns "from" school.