In exceptional circumstances, a teacher or a non-teaching employee of a school may be granted leave not exceeding 18 months; provided the whole case is reported to the Board with a concrete proposal which shall have to be approved by the Board. For details see Clause 5 of GO No. 1541-Edn (S) /21-2/77, dated 15.12.1977
But as this is a case of past, I don’t think your colleague would be benefited now. Anyway, consult your HM for details.