In the spirit of the schools are like factories analogy, which seems to revolve around that both use bells, here's my analogy to replace it. Feel free to ad more in comments.
Schools are like boxing matches because:
...they open end close with bells.
...at the end of each segment, you are judged on your performance
...not everybody finishes
...there's a lot of cheating that goes on
...you have to do a lot of specific training to succeed
people believe that members of the opposite sex are an impediment to
success in the endeavor or at the very least cause distractions that
give you less chance at success.
...the person who isn't allowed to throw punches is outnumbered by the people who can
...somebody's always complaining about not being scored fairly
...state regulations regarding it vary widely
...the people engaged in the act of doing it are rarely the ones who make the real money involved
...it looks better in movies than in real life