How about a general donation in honor of "Mr...Ms....."
I have many teachers in the family and because they receive so much they "regift" the majority.
This way if you give it to the school or to a local charity that would be appropriate maybe they'd find that more thoughtful and it would cost you less than even individual candles.
For my DD's one teacher either a CD with photos from the year so far of school events, a donation to something she is a part of, or a cert. for a manicure