There is laughter when someone overdoes a classifier, dramatizing a car so big it becomes a rolling stage prop. There is quiet concentration when another student wrestles with non-manual signals — the tiny, essential eyebrow tilt that turns a statement into a conditional, the pursing of lips that narrows meaning. Corrections are gentle, offered as adjustments of rhythm rather than verdicts: a tilt of the head, a slight exaggeration of an expression, "try it like this," signed with an encouraging smile.