Well most people tell you to go for your interest and follow your passion but how can a high school student tell if he likes chemical engineering better than metallurgy or mechanical better than civil. Since you are considering all the branches, that is a good thing because there are oppurtunities in every branch otherwise they would not be running. So I believe in choosing the best institute even with a lower branch hence 

IIT Roorkee Metallurgy > IIT BHU Civil/Chemical > Other middle and lower IITs (any branch frankly)