Here are the scores and percentiles for the ACT 1967-68.  These percentiles
are based on 1,755,542 test takers.

   Inasmuch as a score of 32 represented the 99.9 percentile, the booklet
does not include the percentiles for the scores ranging from 33-36.

 Standard Score        Percentile         Percentile
 (composite)           Composite          English

     32                  99.9               99.9+
     31                  99.6               99.9
     30                  98.9               99.8
     29                  97                 99.3
     28                  95                 98
     27                  92                 96
     26                  87                 93
     25                  82                 89
     24                  76                 84
     23                  69                 78
     22                  62                 71
     21                  55                 63
     20                  47                 55
     19                  40                 46
     18                  33                 38
     17                  27                 31
     16                  22                 25
     15                  17                 20
     14                  13                 16
     13                  10                 13
     12                   7                 10
     11                   5                  8
     10                   3                  6
      9                   2                  4
      8                   1                  3

Mean score:         20.1
Standard Deviation:  5.1

Note: The composite score was the average of the four subtest scores (Math, 
Social Studies, Natural Sciences, English). It is not clear how they rounded 
the scores however. A 29.25 average was likley rounded down to a 29, but they 
don't say how a 29.5 would have been rounded, up or down. To avoid this 
issue, the booklet's authors merely provide a straightofrward example of 4 
scores: 25,19, 26,22. This equals 92, or an average of 23 without rounding 
necessary.
   In case someone from that era is interested in the subtest means and 
standard deviations, here they are.

   English         (mean, 19.0, standard deviation, 5.1)
   Math                  (19.7, 6.6)
   Social Studies        (20.6, 6.3)
   Natural Sciences      (20.5, 6.1)

   Composite             (20.1, 5.1)