current page id tag

on my site i’m working on https://chadwick.fbsdhosting.com/school
i was wondering if there was a way to determine which page is being viewed and change the css style of the link refering to the current page.
the sidebars and header are part of an include that gets included in to each of the pages.
I was thinking about using php to find out what page it is and then change the code. But my php skills are lacking and if someone knew of an easy solution i’d be very pleased.