A class with 450 would usually be a freshman year class about one of the basics..ie..English,Biology,Algebra..etc. Most kids would not be 21. Good bet the odds are there would not be a single CHL in the class except the teacher.
All it takes is one good guy with a gun to end a potential slaughter... What if it's the 23 year old Marine / Army veteran who is in their first year of college after fighting for OUR country for 4 years so they could afford to go to college on the GI Bill? You have to keep an open mind here too and not automatically assume that college freshmen are 18 or 19 year olds.