A First, it will be a good idea to liaise with your English as an additional language teacher to ask what information she or he has about the child.
Many schools have good recording systems for new arrivals which ask parents and carers for information about their schooling and health. He's been in your school for only five months, and if he is new to the UK, he may still be in the silent period: actively listening, but not yet speaking.
Does he respond to you and others with body language, physical actions or eye contact? Are there any older children in the school who speak Serbo-Croat who could talk to him? Are there opportunities for play and role play in your classroom where he might begin to join in with a group? Do you have picture books with predictable language, story props and other visual aids to support reading? A discussion with his parents will be important - but initially an EAL assessment rather than a special needs assessment may be indicated. The Portsmouth ethnic minority achievement service website has a useful checklist for thinking about children whose English is an additional language and who may have special needs. It contains other helpful resources as well. See www.blss.portsmouth.sch.uksenfilterq.shtmlNoNotop