The SENCo is likely to want evidence from this kid’s subject teachers, before taking any action. Evidence that the teachers can’t read the child’s handwriting. Has there been a parents evening recently, and if so, did any teacher mention the issue?
When did the problem start? If handwriting was OK in, say, Year 9, school may insist that he hand writes. Unless he can type quickly and accurately there’s no point in issuing a laptop for use in lessons, which the school probably can’t afford anyway at this time of the year.