The following is another option:

Code:
SQL> select t1.*,
  2     dense_rank() over (partition by hier_level
  3                     order by standard_source, title,year_adopted) group_id
  4  from t1;

HIER_LEVEL STANDARD_SOURCE TITLE                     YEAR_ADOPTED   GROUP_ID
---------- --------------- ------------------------- ------------ ----------
         1 FL              Sunshine State Standards          2006          1
         1 FL              Sunshine State Standards          2007          2
         1 GA              Performance Standards             2004          3
         1 GA              Performance Standards             2004          3