In this case, the singer is addressing a girl (whom he obviously loves) who is "putting on airs", or pretending to be of higher social status than he. He knows the truth, and understands her background, and when he says "I'm gonna take you down" he means to (as we say in the US) knock her down a peg, to bring her back to reality. He will ultimately make her aware of her true background and expose her to her high-class friends. But it also means he loves her for what she is, and not what she pretends to be.
- For Teachers