This survey is based on a dump of spell usage done a server (I don't know which) on April 1, 98, one week after Renaissance went live. The dump is available here, raw except for having been split into schools and labelled by level. The repot shows how often spells are attempted, how often the casting succeeds, and other potentially useful data. The average spellpower is new in Renaissance and looks kind of glitchy, so I haven't really relied on it as a measure of spell effectiveness.

A 'cast' is defined as a successful cast (a cast which passed simple ability, eligibility, and targetting checks and thus used reagents). Touch attack spells use the physical attack code (note that the 'casts' field is always 0 since it doesn't run through that bit of code) and always use reagents, so for those spells a 'cast' is defined as an attempt.

Number of spells/skills

Qor Shal'ille Faren Kraanan Riija Jala Weaponcraft
all levels 23 25 19 25 19 5 13
level 1 3 2 2 2 5 1 2
level 2 3 6 4 4 4 1 3
level 3 4 4 4 7 4 1 3
level 4 7 6 3 6 2 1 3
level 5 5 5 4 5 3 1 1
level 6 1 2 2 1 1 0 0

Level of Usage (the popularity factor)

Qor Shal'ille Faren Kraanan Riija Jala
all levels 24102 43478 29976 94551 15809 1457
level 1 5385 15462 9482 14226 8795 219
level 2 8063 3675 13640 31526 5999 515
level 3 8141 5362 1819 25134 437 624
level 4 1565 10434 1930 16608 572 97
level 5 948 8525 3060 6573 6 2
level 6 0 38 45 0 0 0

Average usage per spell (the 'dead weight' factor)

Qor Shal'ille Faren Kraanan Riija Jala
all levels 1048 1739 1578 3782 832 291
level 1 1795 7731 4741 7113 1759 219
level 2 2688 610 3410 7882 1500 515
level 3 2035 1341 455 3591 109 624
level 4 224 1739 643 2768 286 97
level 5 190 1739 765 1315 2 2
level 6 0 19 23 0 0 0

Qor:

24102 casts total. 23 spells. 1048 casts per spell (this number is something of a 'coolness rating' for the school).

1: 5385 casts. 1795 per spell.

2: 8063 casts. 2688 per spell.

3: 8141 casts. 2035 per spell.

4: 1565 casts. 224 per spell.

5: 948 casts. 190 per spell.

Shal'ille:

43478 casts total.

1: 15462 casts. 7731 per spell.

2: 3675 casts. 610 per spell.

3: 5362 casts. 1341 per spell.

4: 10434 casts. 1739 per spell.

5: 8525 casts. 1705 per spell.

6: 38 casts. 19 per spell.

Faren:

29976 casts total.

1: 9482 casts. 4741 per spell.

2: 13640 casts. 3410 per spell.

3: 1819 casts. 455 per spell.

4: 1930 casts. 643 per spell.

5: 3060 casts. 765 per spell.

6: 45 casts. 23 per spell.

Kraanan:

94551 casts total.

1: 14226 casts. 7113 per spell.

2: 31526 casts. 7882 per spell.

3: 25134 casts. 3591 per spell.

4: 16608 casts. 2768 per spell.

5: 6573 casts. 1315 per spell.

6: 0 casts. 0 per spell.

Riija:

15809 casts total.

1: 8795 casts. 1759 per spell.

2: 5999 casts. 1500 per spell.

3: 437 casts. 109 per spell.

4: 572 casts. 286 per spell.

5: 6 casts. 2 per spell.

6: 0 casts. 0 per spell.

Jala:

1457 casts total.

1: 219 casts.

2: 515 casts.

3: 624 casts.

4: 97 casts.

5: 2 casts.

A partial transcription of the raw dump into a more readable format:

(I stopped when I realized that it was of limited use)

Qor:

level name casts average spellpower new
1 darkness 4066 -5
1 unholy weapon 554 50
1 unholy resolve 765 44
2 Kara'hol's curse 1775 58
2 detect good 389 37
2 acid touch 5899 N/A
3 enfeeble 3400 -28
3 fade 637 56
3 hold 4021 3
3 animate 83 54
4 defile 178 53
4 curse weapon 0 0
4 poison fog 95 49 *
4 swap 195 52
4 shadow rift 0 0 *
4 Shal'illebane 326 56
4 vampiric touch 771 0
5 blind 414 69
5 death link 88 87
5 invisibility 445 54
5 nodeburst 1 54
5 blood inheritance 0 0 *
6 gaze of the basilisk 0 0