For the Gb at the same time worldly people including your teachers and classmates are:
part of Satan's system and have Satan's mind and are "against" us (literally, they said that in the final talk)
they are also:
very educated people who will stop a biology class to let a student talk about particular beliefs, ask you about the kingdom, respect you because you stood for your belifs...
It just can't be both. Either wordly people are bad and the JW should not try to evangelize them by word because obviously they won't listen and will attack the JW, or they are good and so there's no problem to spend time with them after school, work or having meals with them.