St. Thomas H.S. School had its simple origin with its Kindergarten Classes in the year 1974 in the Catholic Church Campus at Barnagar. The earnest desire of the parents and students of the Town and surrounding villages was the motivating force to develop it into a co-educational higher secondary school. The school was provisionally affiliated to C.I.S.C.E in 2008, and it received permanent affiliation in 2011.

The School bears the name of St. Thomas, one of the twelve apostles of Jesus Christ. St. Thomas came to India in 52 A.D with a mission to preach and teach the good news of Jesus Christ. He died as a martyr at Mylapore in Madras, but his mission and vision continues and still leads many from darkness to the light (THAMASOME JYOTHIGAMAYA).