WITH T AS(
    SELECT
        student_code,
        AVG(total_score) OVER() AS avg_score
    FROM
        total_scores
)
UPDATE
    total_scores
SET
    passed =
    CASE
        WHEN total_score >= avg_score THEN TRUE
        ELSE FALSE
    END
FROM
    T
WHERE
    total_scores.student_code = T.student_code