Ehhh... there are a lot of them... ost are with school work though.
This is an offshoot of Coupled Union - Tick Tock, with him married to Setsuna, It is mentioned Ami tutors him in her free periods.
R-AA 'Tick Tock Chaos' by Multiple - [Status=Not Complete] - [Last Dld=04/21/2007] - [Size=63kb]
Setsuna asks Ami to tutor Ranma in.
R-SM 'A Dark Moon Rising' by deathgeonous - [Status=Not Complete] - [Last Dld=08/31/2007] - [Size=103kb]
Had it been continued, Ranma was being nagged into getting Ami as a tutor in.
R-SM 'Family Socializing' by Lumias - [Status=Not Complete] - [Last Dld=09/12/2006] - [Size=92kb]
In the Silver Millenium, past incarnation of Ami tutored past incarnation of Ranma.
R-SM 'Knights of a Silver Moon' by Travis Grant - [Status=Not Complete] - [Last Dld=08/08/2002] - [Size=110kb]
Ami is convinced to tutor Ranma by mother, who is friend of Nodoka.
R-SM 'No Chance for Fate' by Tribun - [Status=Not Complete] - [Last Dld=10/05/2008] - [Size=156kb]
Ami tutors Ranma in exchange for martial arts lessons.
R-SM 'Youma 12' by James Thomas - [Status=Complete] - [Last Dld=03/01/2005] - [Size=879kb]
Runner up. Setsuna convinces Nabiki into tutoring Ranma on social graces. Not tutored by a senshi, but a senshi convincing someone to tutor him.
R-SM 'Finding an Anchor' by TheGrum - [Status=Not Complete] - [Last Dld=07/12/2007] - [Size=349kb]
Runner up. Ranma tutored by a member of the dark moon family.
R-SM 'Ranma, Mage of the Darkness' by HistorianoftheKais - [Status=Not Complete] - [Last Dld=11/02/2008] - [Size=357kb]
Runner up. Ami tutors Ryoga.
R-SM 'Twin Dragons Under Moonlight' by Ben Bradley - [Status=Not Complete] - [Last Dld=07/08/2004] - [Size=731kb]
I vaguely recall Rei tutoring Ranma on centering, meditation, and shintoism, and other such items in a story, but cannot think of where I came across that. I think I can also recall it including magic and mysticism.
In most cases, except possibly Ami or Setsuna... I cannot really see any of the Senshi tutoring Ranma on academics... Maybe Makoto on cooking... but the rest... Minako and Usagi's grades are not so good, I think I remember once Makoto stating her grades were average. *Normally* Saturn is too young to help him, maybe a scene in 'Sound Hearts'. Haruka is physically oriented, so would not be able to help there.
I do know it is specifically mentioned Michiru taught him an instrument and he calls her sempai in.
R-SM 'Chaos and crystal tokyo' by Master Magi - [Status=Single File] - [Last Dld=09/21/2005] - [Size=429kb]