Hi Janardhan, your best bet is to look at the Govt Website www.gov.uk/.../sponsorship-information-for-employers-and-educators and their specific Guidance. I don't work in a School but I assume you will need to sponsor a teacher under the Skilled Worker Route. Try these documents as your starting points.

www.gov.uk/.../workers-and-temporary-workers-guidance-for-sponsors-part-2-sponsor-a-worker

www.gov.uk/.../workers-and-temporary-workers-sponsor-a-skilled-worker

www.gov.uk/.../workers-and-temporary-workers-guidance-for-sponsors-part-3-sponsor-duties-and-compliance