A Louisiana inmate accused of engaging in sex acts near an elementary school while on a work detail has pleaded guilty to a 'crime against nature'.

Some students and teachers at Princeton Elementary School witnessed William A. Wright and two fellow inmates engaged in sexual activity together behind a brush pile in October last year when they were supposed to be clearing bushes and undergrowth at a church near the school.

Wright entered his plea after prosecutors agreed to dismiss a second, less serious charge of obscenity. The 32-year-old also has promised to testify against codefendants Willie James Harris, 42, and Andre Blaze, 29, both of whom rejected the same plea bargain taken by Wright.

The two are charged with both a crime against nature and obscenity, and are scheduled for trial on May 14.

Wright faces up to five years in prison for the crime-against-nature charge but could receive some consideration at sentencing for his cooperation and guilty plea.

Sheriff Larry Deen no longer allows inmate crews to work at or near school campuses except during summers when students are not present.