Why is Tsukune allowed into the monster school, in Rosario+Vampire? So Tsukune's father just finds someone drop a school admission letter, and give it to Tsukune. And then he goes into a monster school, and where the magic to stop humans doesn't work, and becomes a normal student. Am I the only one who finds this weird?

Is there any reason he was allowed in the school? Surely the teachers/headmaster would realise he is not a monster, and that he is using someone else's admission letter?
The trick to this is, that noone in the school knows he is human except


   the headmaster, who dropped his letter of admission in the first episode  


and maybe the bus driver, who is revealed to be:


   Nurarihyon the supreme commander of all monsters in the last episode of the 2nd season manga. 


additionaly to the end of Capu 1 (it's their Season)  


   he almost dies and Moka Akashiya turns him into a part-vampire to save his life  


The plot device used for this is, that in School no one is allowed to show their true form, but have to disguise as humans. This allows him to wander freely in this school for monsters.

At the same time of the revelation on who the Bus Driver is, the true reason is also revealed:


   Nurarihyon (aka the Bus Driver, aka the supreme commander of all monsters) wants Tsukune to be the next headmaster of the school of monsters.