When the students returned, all safe and unharmed, the teacher was more concerned for their well-being, not angry about their off-campus adventure.
When the students returned, all safe and unharmed, the teacher was more concerned for their well-being than angry about their off-campus adventure.
When the students returned, all safe and unharmed, the teacher was more concerned for their well-being, not angry about their off-campus adventure.
When the students returned, all safe and unharmed, the teacher was more concerned for their well-being than angry about their off-campus adventure.
The idiom "more X than Y" shows a contrast of amount, and the construction "X, not Y" shows an absolute contrast. Both are correct, but if the word "more" appears in the first half, we have to use the former idiom, not the latter.