Xは、この学校で日本語を勉強したんだって。
Is this the -te form of the copula? Haven't encountered it so far.
Xは、この学校で日本語を勉強したんだって。
Is this the -te form of the copula? Haven't encountered it so far.
って is used as a quotative particle in casual speech. See: と、て、って Quoting Particle Usage
A sentence can sometimes end with と/って, and it usually means "I heard ~" or "They say ~". So you can think that 言ってた or 聞いた is omitted after it.
The sentence means "I heard X learned Japanese at this school."