PHP Security

I have been studying PHP all summer because I wanted to put some PHP code on my schools web site. I got to school and went to the web design teacher. I asked him if they had installed PHP on their server. He said that the district thinks that it would be a HUGE security risk and that people at my school would try to hack into the server (what bull). Anyway, can you give me some tips to make the server secure? Any help would be appreciated!