If you need help on how to rank your character, here's info on the star ranks-


*ONE STAR MEISTERS AND WEAPONS*

-Weapons and Meisters who have collected less than 50 souls

-Can only borrow level one and two books

-Can only take level one or two missions

**TWO STAR MEISTERS AND WEAPONS**

-All members of Spartoi are automatically 2-star rank, students who promote to 2-star rank are automatically members of Spartoi

-Weapons and Meisters who have collected more than 50 souls

-Can only borrow level one or two books

-Can only take level one, two and some level three missions

-Can come into the Death Room without permission

***THREE STAR MEISTERS AND WEAPONS***

-Weapons and Meisters who have collected 99 souls and one witch soul, and all staff members

-Can borrow all kind of books

-Can take missions up to level 3 and some level 4 missions

-You're allowed to enter the underground (The jails, the secret vault, etc)

***FOUR STAR RANK ***

-This is the highest rank that you can obtain. This is the rank for Death's personal staff(Personal Death Scythe, Personal Secretariat also his son is 4 star rank)and the pro's in their category (Meisters, Weapons and Witches)

-In each category is only one pro

-Have permission to go everywhere in the school

-May take all kind of missions

-May take all kind of books

-Are chosen by Death himself

-May enter the entire underground

EDIT!
Demon Weapons are not included in the Star ranking system, and are only placed into two categories: a normal Demon Weapon or a Death Scythe. The strength of a Weapon though, can vary as much as Meister's.