We have daily phone calls from parents identifying concentration at school as a problem for their child. There can be all sorts of contributing factors, which is why a proper assessment of the situation is always a good idea. Mat time is often a tricky time as kids may have issues with:
* touch (eg hypersensitive to other kids touching them, constantly seeking tactile input for calming),
* movement (eg need movement to stay alert, difficulty maintaining their postural control),
* auditory or visual processing (eg easily overwhelmed in a more confined area)
* and there are more reasons as well, eg language comprehension.
Tactile avoiders are better with a small stool or a carpet square so they have their own space with less 'risk' of them being touched.
For children who are easily overwhelmed by noise you can try setting up a quieter place for them to go, eg a beanbag a little bit separate from the group but still within vision and hearing distance from the teacher.
These are just some simple, quick strategies which can give instant improvements and can be considered 'first line of defence'. The important thing is to identify the underlying issue and this is best done by watching the child during mat time with your 'sensory processing hat' on. This means watching carefully how they react to different sensory stimuli. There are many more factors at play and strategies to consider, and this is where you would call on an OT to give you a hand.