What social class was a summoner in the Medieval times?

Answer 1

A Summoner was a man who delivered summonses for alleged public sinners to appear at the Archdeacon's ecclesiastical court when accused of public immorality. The job offered opportunities for serious abuse such as bribery, extortion, and especially blackmail of those who went with prostitutes. Source: http://academic.brooklyn.cuny.edu/webcore/murphy/canterbury/9summon.pdf

Answer 2

the Summoner would be grouped under the ecclesiastical middle class. He was not poor, but his power was only so great, and his authority was minimal. As a summoner his job was to summon sinners to trial before a court of the church.