Write SQL query to solve given problem: Calculate the average score per university under Alumni criteria in 2008.. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT AVG(T2.score) FROM ranking_criteria AS T1 INNER JOIN university_ranking_year AS T2 ON T1.id = T2.ranking_criteria_id WHERE T1.criteria_name = 'Alumni' AND T2.year = 2008