You could also use
SELECT GroupID,
SomeValue
FROM tablename
ORDER BY MAX(CRYPT_GEN_RANDOM(4)) OVER (PARTITION BY GroupID),
GroupID, --Just in case 2 groups get the same random number
SomeValue;
You could also use
SELECT GroupID,
SomeValue
FROM tablename
ORDER BY MAX(CRYPT_GEN_RANDOM(4)) OVER (PARTITION BY GroupID),
GroupID, --Just in case 2 groups get the same random number
SomeValue;