Как победить триггер

ALTER TRIGGER triggerForChildren ON [dbo].[Childer] --Purchasing.PurchaseOrderHeader
AFTER INSERT
AS
IF ((SELECT 
        COUNT(*) 
    FROM [dbo].[Childer] c 
    JOIN inserted AS i ON c.id = i.id 
        JOIN [dbo].[Class] AS cl ON cl.id = c.ClassID
    WHERE cl.Class != 0 and cl.id = i.ClassID
    ) > 30)
BEGIN
    RAISERROR ('Превышено допустимое количество учеников в классе.', 16, 1);
    PRINT ('4o proishodit');
    ROLLBACK TRANSACTION;
    RETURN
END;

declare @i int = 1, @max int = (SELECT COUNT(Class) FROM Class where Class != 0), @name varchar(30), @last varchar(30), @classID int, @bd date 
declare @n tinyint = 1, @t int
while @i <= 300 --@max
BEGIN
    set @n = 1
    
        set @name = 'Name ' + CAST(@i as varchar)
        set @last = 'LastName ' + CAST(@i as varchar)
        set @t = rand()*datediff(day, '1996-01-01', '2003-01-01')
        set @bd = dateadd(day, @t, '1996-01-01')
        set @classID = (SELECT id FROM Class WHERE CEILING(rand()*(10-1)) = id)
        insert into Childer(Name, LastName, BirthDate, ClassID, [NumberAtClass])
        values(@name, @last, @bd, @classID, @n)
 
    set @i +=1
END

alter trigger triggerForChildren on [dbo].[Childer]
after insert
as
begin
 set nocount on;
 
 if not exists(select * from inserted)
  return;
 
 if exists(
   select 
    * 
   from
    [dbo].[Childer] c
   where
    exists(select * from inserted where ClassId = c.ClassID)
   group by
    c.ClassID
   having
    count(*) > 30
  )
  begin
    raiserror ('Превышено допустимое количество учеников в классе.', 16, 1);
    rollback transaction;
    return;
  end;
end;