Filter org file exportation according to entry tags (or properties)?

I mainly use org-mode to write announcements to my students, recently I usually write files with > 16 entries (headings), some of them are very, very important and some of them are not. What I'm currently doing is: I create 2 files, one includes all the entries, and the other one includes only the most important ones (so that lazy student will read them) and then export both as HTML. Is there is anyway to automate that filtration process?

See `org-export-exclude-tags` or "EXCLUDE_TAGS" exprot setting 13.2 Export Settings section of the manual).