  Multimodal Learning Analytics (MMLA) innovations make use of rapidly evolving
sensing and artificial intelligence algorithms to collect rich data about
learning activities that unfold in physical learning spaces. The analysis of
these data is opening exciting new avenues for both studying and supporting
learning. Yet, practical and logistical challenges commonly appear while
deploying MMLA innovations "in-the-wild". These can span from technical issues
related to enhancing the learning space with sensing capabilities, to the
increased complexity of teachers' tasks and informed consent. These
practicalities have been rarely discussed. This paper addresses this gap by
presenting a set of lessons learnt from a 2-year human-centred MMLA in-the-wild
study conducted with 399 students and 17 educators. The lessons learnt were
synthesised into topics related to i) technological/physical aspects of the
deployment; ii) multimodal data and interfaces; iii) the design process; iv)
participation, ethics and privacy; and v) the sustainability of the deployment.
