だけでなく and ばかりか: adding facts and exceeding expectations
Compare two expressions that retain one fact while adding another. Check their connecting forms, the emphasis of も and まで, and the contrast with an expression that rejects the first item.
Both parts remain true
この店はパンだけでなく、スープも売っています。 means that this shop sells soup as well as bread. Despite なく, the sentence does not deny that bread is sold.
Verbs and adjectives can connect too. この部屋は広いだけでなく、明るいです。 adds brightness to spaciousness. Both qualities describe the same room.
ばかりか goes beyond what was expected
彼は遅れたばかりか、資料も忘れてきました。 means that he was late and, on top of that, forgot to bring the documents. The first fact is already noteworthy, and the second adds to it.
The expression also works with positive outcomes. この方法は時間を節約できるばかりか、費用も減らせます。 means that this method can not only save time but also reduce costs. Do not memorize ばかりか as an expression reserved for bad events.
Connecting forms and the scope of negation
Nouns connect as 学生だけでなく or 学生ばかりか, while na-adjectives use forms such as 便利なだけでなく and 便利なばかりか. A following も or まで identifies the added item; まで can further suggest an unexpected extent.
パンではなく、スープを買いました。 corrects the choice: the speaker bought soup, not bread. パンだけでなく、スープも買いました。 says that both were bought, so the presence of だけ makes a major difference.
Quick check: In 先生だけでなく、学生も参加しました。, did the teachers not attend?
Show the answer and why
The teachers attended, and the students attended too. だけでなく retains the first fact and extends the group of participants to include students.