Despite general agreement that laughter is crucial in social in- teractions and cognitive development, there is surprisingly lit- tle work looking at its use through childhood. Here we inves- tigate laughter in middle childhood, using a corpus of online calls between child and parent and between the (same parent) and another adult. We focus on laughter mimicry, i.e., laugh- ter shortly following laughter from the partner, and we com- pare mimicking and non-mimicking laughter in terms of dis- tribution and acoustic properties using spectrotemporal modu- lation measures. Our results show, despite similar frequencies in laughter production, different laughter mimicry patterns be- tween Parent-Child and Parent-Adult interactions. Overall, in comparison with previous work in infants and toddlers, our results show laughter mimicry is more balanced between par- ents and school-age children. At the acoustic level, we observe differences between mimicking and non-mimicking laughter in children, but not in adults. Moreover, we observe signifi- cant differences in laughter acoustics in parents depending on whether they interact with children or adults, which highlights a strong interlocutor effect on laughter mimicry.