Hi,
My 4yr old son is deaf so I now have a totally different perspective on what it would be like to have a hearing impaired child in my class!
First off, I suggest you talk to the parents. Do they do sign with him at home? do they want him to learn it? We came up against a lot of resistance with County (Oxfordshire) that we were going to go down the signing route. They refused to support anything

- it won't help him integrate with the hearing community. Signing is tricky as the sentence structure is different to English but you could do sign supported English - signing specific words to highlight the point of a sentence.
If he is not already on SEN, I would suggest putting him on IA and then consulting with a county funded teacher for the deaf. They may provide a loop or radio aid system for you to use in the classroom. It makes life a lot easier for them as the teachers voice is amplified above the background noise.
Do be prepared for him getting more tired than other children, listening is hard work. He may need a bit of down time in order to refocus.
Get in touch with your local branch of NDCS (National Deaf Children's Society) they have fantastic resources and support. Forest books do a range of resources that may help but it depends on which route you take with the signing.
Enjoy,
Lucy