Training (Optional Rule) (DMG)

Some DMs do not like the idea that a character can instantly advance in level simply by acquiring enough experience points. To their minds all improvement is associated with schooling, practice, and study. Others argue that characters are constantly doing these things to increase their ability so formal schooling is not required. Either case may be true.
The DM might choose to require characters to train before they increase in level. To train, a character must have a tutor or instructor. This tutor must be of the same class and higher level than the one the character is training for. Thus, a 7th-level fighter training for 8th-level must be taught by a 9th-level or higher fighter. The tutor must also know the appropriate things. Fighters specialized in a given weapon must find a tutor also specialized in that weapon. Mages seeking to study a particular spell must find a tutor who knows that spell. A thief seeking to improve his lockpicking must find a higher-level tutor more accomplished in lockpicking.
Since not all characters are suited to instructing others, any player character who attempts to train another must make both a Wisdom check and a Charisma check. If the Wisdom check is passed, the player character possesses the patience and insight to nurture the student. If the Charisma check is passed, the character also has the wit, firmness, and authority needed to impress the lessons on the student. If either check is failed, that character is close, but just not a teacher. If both checks are failed, the character has absolutely no aptitude for teaching. Alternatively, the DM can dispense with the die rolls and rule for each player character, based on his knowledge of that character's personality. It is assumed that all NPC tutors have successfully passed these checks.
Second, the character must pay the tutor. There is no set amount for this. The tutor will charge what he thinks he can get away with, based on either greed or reputation. The exact cost must be worked out between player character and tutor, but an average of 100 gp per level pr week is not uncommon.
Finally, the player character must spend time in training. The amount of time required depends on the instructor's Wisdom. Subtract the Wisdom score from 19. This is the minimum number of weeks the player character must spend in training—it takes his instructor this long to go through all the lessons and drills. At the end of this time, the player character makes an Intelligence or Wisdom check, whichever is higher.
If the check is successful, the lessons have been learned and the character can advance in level. If the check is failed, the character must spend another week in training. At the end of this time, another check is made, with a +1 applied to the character's Intelligence or Wisdom score. The results are the same as above, with each additional week spent in training giving another +1 to the character's ability score. This +1 is for the purpose of determining the success or failure of the check only. It is not permanent or recorded.
One obvious result of the training system is the development of different academies that specialize in training different character classes. Because of their importance in the adventuring community, these academies can become quite powerful in the lives of the player characters. Imagine the disastrous effect should one of the player characters be blacklisted by his appropriate academy. Although the DM should not abuse such power, the player characters should treat such institutions with care and respect.