is it better to focus on an expertise or branch out?

I just got accepted as an assistant for programming lab class in my university. basically, I got training on wide area of basic stuff so I can teach student who learns different things(php, jsp,java,css,javascript, mysql, sql server,hibernate,unity etc) As you can see, it's pretty diverse, I was pretty happy about it, it got me a bit of overwhelmed because I always had a hard time to memorize new syntax. This got me thinking though, is there any good at all in learning those wide varieties of subject? So, what do you think? Would you rather focus on one area of expertise, or would you rather branch out? :D