You need an expression that returns "Fall_2009" or "Spring_2009", and then group on that expression. eg:
-- identify each pattern individually w/ a case statement
SELECT
CASE
WHEN column_x LIKE '%Fall[_]2009' THEN 'Fall 2009'
WHEN column_x LIKE '%Spring[_]2009' THEN 'Spring 2009'
END AS group_by_value
, COUNT(*) AS group_by_count
FROM Table1 a
GROUP BY
CASE
WHEN column_x LIKE '%Fall[_]2009' THEN 'Fall 2009'
WHEN column_x LIKE '%Spring[_]2009' THEN 'Spring 2009'
END
or
-- strip all characters up to the first space or dash
SELECT
STUFF(column_x,1,PATINDEX('%[- ]%',column_x),'') AS group_by_value
, COUNT(*) as group_by_count
FROM Table1 a
GROUP BY
STUFF(column_x,1,PATINDEX('%[- ]%',column_x),'')
or
-- join to a (pseudo) table of pattern masks
SELECT b.Label, COUNT(*)
FROM Table1 a
JOIN (
SELECT '%Fall[_]2009' , 'Fall, 2009' UNION ALL
SELECT '%Spring[_]2009', 'Spring, 2009'
) b (Mask, Label) ON a.column_x LIKE b.Mask
GROUP BY b.Label