Hello! I agree with Darren. It would depend on the context of the sentence. If you were only talking about age then "she's two years younger than me." would be correct. But f you were talking about being two years younger in terms of going to school then you would say "She is two tears behind me". I hope that helps!

Not quite. Younger refers to age. 'Behind' could mean that she is two classes behind e.g. grade 4 and grade 2, but she could be old for her class or young for her class, which would mean that she is not 2 years younger. 'Behind' talks about someone who is doing something who has not yet reached your level or standard.

Well, not exactly. She could be two years behind you in school (you are 10th grade, she is 8th grade), but she might not necessarily be two years younger. It's best to stick to "she's two years younger than me" if you are specifically speaking about age. Hope that helps!

Thank you all! :)

Not when you are referring to age; however, we can use this expression commonly for grade levels in school. As in "I'm a senior, but Meghan is two years behind me" or "I graduated in 2007, and my sister was two years behind me."