SQL按varchar中的数字顺序

我有nvachar字段,

select youngestage from table1 
ORDER BY
    CASE WHEN ISNUMERIC(youngestage) = 1 THEN 0 ELSE 1 END,
    CASE WHEN ISNUMERIC(youngestage) = 1 THEN CAST(youngestage AS INT) ELSE 0 END,
   youngestage

 0
 1
 1.5
 10
 11
 12
 14
 2
 3

将nvarchar值'1.5'转换为数据类型int时,转换失败。我们怎么能这样订购

YoungestAge
 0
 1
 1.5
 2
 3
10
11
12
14