Two full houses of cheering, screaming schoolchildren were treated to opera yesterday at the Kennedy Center's Eisenhower Theater - "Jumping Frog of Calaveras County," composed by Lucas Foss from the Mark Twain story. It was the second event in this week's National Children's Arts Festival.

Opera New England, a regional program of Sarah Caldwell's Opera Company of Boston, put on a lively and sylish production in a way that had no trouble capturing the two morning audiences. By the time the tricky stanger's onstage cheating had been discovered and he had been captured, several excited children were shouting at the man holding the shotgun, "Shoot him! Shoot him!"

The good-looking production, brought down from Boston, is the work of John Degan. Caldwell did the direction, turning the conducting over to William fred Scott, who handled the score smartly. The 18-piece orchestra was expert, and no wonder, since its concertmaster was Richard Burgin, for years the concertmaster of the Boston symphony.

The Twain folk tale about the sneaky stranger feeding buckshot to Smiley's prize frog - "jumped 14 feet and caught 14 files!" - makes great entertainment in the expert singing of Joseph Evans as Smiley, Eunice ALberts as Lulu and Robert Trehy as the stranger. They were strongly assisted by Jason Byce's Uncle Henry, David Evitts and Mathew Murray taking turns as the Guitar Player, and William Fleck and Michael HUme as the crapshooters.

And the Eisenhower proves to be an outstanding theater for intimate opera.