And here is the quote (originally from the Random House Unabridged Dictionary):

“Although it is frequently claimed that different should be followed only by from, not by than, in actual usage both words occur and have for at least 300 years. From is more common today in introducing a phrase, but than is also used: New York speech is different from (or than) that of Chicago. Than is used to introduce a clause: The stream followed a different course than the map showed. In sentences of this type, from is sometimes used instead of than; when it is, more words are necessary: a different course from the one the map showed. Regardless of the sentence construction, both from and than are standard after different in all varieties of spoken and written American English. In British English to frequently follows different: The early illustrations are very different to the later ones. The use of different in the sense “unusual” is well established in all but the most formal American English: The décor in the new restaurant is really different. ”

Bottom line: Either is correct. Teachers can sometimes be wrong