訓 く(む),くみ,-ぐみ ・ 音 ソ
Sino-Vietnamese: tổ
Thread 糸 gives the meaning and 且 the sound: strands braided together into one group, so it means group, class or assemble (Han Viet to, as in to chuc = organization).
Stroke data: KanjiVG (CC BY-SA 3.0) — kanjivg.tagaini.net
私は三年二組です。 (わたしはさんねんにくみです)
I am in year three, class two.