How to update a table with sum of values from the table itself and another table in MySQL with WHERE clause

I know there are similar questions to this, but the answers are not quite what I have been looking for. I have two MySQL tables, I’ll say table1 and table2. The fields in table1 are StudentID , Grade and Total_Score. And the fields in table2 are StudentID ,Grade and Total_Score as well. What I want to do is SUM(table1.Total_Score) and add it to SUM(table2.Total_Score). So that Total_Score in table2 is accumulated with scores from table1.Total_Score. I have tried to achieve that with my code below but the scores in table2.Total_Score never accumulate. They stay the same, even though my code gave no error. See my code below.

update table2 o inner join
SELECT op.StudentID,
sum(ot.Total_Score) as Total_Score_ot
 sum(op.Total_Score) as Total_Score_op
FROM table1 ot inner join table2 op on op.StudentID = ot.StudentID
WHERE ot.Grade = 'Grade8'
GROUP BY op.StudentID
) as o1 on o.StudentID = o1.StudentID
SET Total_Score=Total_Score_op + Total_Score_ot


Hmmm . . . I don’t think you need a join in the subquery:

update table2 o inner join
       (select ot.StudentID, sum(ot.Total_Score) as Total_Score_ot
        from table1 ot
        where ot.Grade = 'Grade8'
        group by ot.StudentId
       ) ot
       using (studentid)
    set o.Total_Score = o.Total_Score + Total_Score_ot;