I would recommend you start by having a look on the National Deaf Children’s Society website but it might be also worth first establishing the exact nature and functionality of this child’s hearing in both ears. Depending on what this is, classroom/staff adaptations may be as important as an auditory skills programme e.g. does he use a radio aid? are they being mindful of background noise? Mild-moderately severe sensorineural covers quite a range of hearing loss and it may be different in both ears.
It is also now very much preferred that the term ‘Deaf/deafness/hearing loss’ is used in place of ‘hearing impairment.