select
                       CASE WHEN Age > 15 AND Age < 19 THEN '16to18' when Age > 18 AND Age < 25 THEN '19to25' WHEN Age > 24 THEN 'Over25' else 'Uknown' END AS Age
                       , COUNT(someidfield)
                      FROM          dbo.Learner
                                               WHERE      (UserID = '0713cb98-0c31-47bb-90f9-7fd521897455') AND (Added > CONVERT(DATETIME, '06/05/2012 00:00', 103)) AND
                                                                      (Added < CONVERT(DATETIME, '12/05/2012 23:59', 103))
group by CASE WHEN Age > 15 AND Age < 19 THEN '16to18' when Age > 18 AND Age < 25 THEN '19to25' WHEN Age > 24 THEN 'Over25' else 'Uknown' END