<p>Math 55 is not hard because of the material it covers. There are many courses at Harvard (and probably even at most state schools) that cover much harder material. It’s considered hard because it’s intended for freshman, which means that the successful student in that class will need to have taken probably a few years of university level math courses while in high school and will need to have extensive experience with proofs. It’s a good course for former IMO participants, for instance, because most of these people will have had intensive coaching and training throughout high school (and almost always junior high as well).</p>
<p>There are extremely few courses offered that have such bizarre prerequisites because it’s very rare for someone to have figured out what they want to be in life at such an early age and to have dedicated so much time in pursuit of this choice.</p>
<p>If Harvard Law were analogous, then students at Harvard Law would be expected upon entry to have mastered the first few years of material taught at other good law schools. I don’t know if this is the case.</p>