QUESTION

Does completing a masechet of Mishnayot with the Artscroll commentary constitute a significant enough accomplishment for a 14-year-old to make a siyum and eat meat during the Nine Days? May he recite the hadran and special kaddish?

ANSWER

If it was a meaningful accomplishment and took ongoing time and investment, then yes.

See Iggrot Moshe Orach Chaim 1:157:

בדבר אם יש להחשיב סעודת מצוה לפטור הבכורים מהתענית ערב פסח ולאכול בשר מר”ח אב עד התענית גם כשמסיימין בחבורה שלומדים מקרא בעיון …אבל מ”מ נראה לע”ד שהדין אמת דאף למוד בעיון הספרים של תורה שבכתב נמי יש להחשיב הסיום סעודת מצוה דהא מצינו דלאו דוקא סיום מסכת ללמד אלא כל מצוה שנמשכה משך זמן נמי יש שמחה בסיומה

Regarding whether to consider it a seudat mitzvah to exempt firstborns from the fast of Erev Pesach and to eat meat from Rosh Chodesh Av until the fast even when they complete a group study of Tanakh with depth… But in any case, it seems to me that the law is correct that even in-depth study of the books of the Written Torah should also be considered a completion worthy of a seudat mitzvah, for we find that it is not specifically the completion of a tractate of learning, but rather any mitzvah that extended over a period of time also has joy in its completion.

See also: https://library.yctorah.org/audio/episode-36-pre-pesach-making-a-siyum-on-abook-of-tanakh