A US sex offender who posed as a 12-year-old boy to enrol in schools has pleaded guilty to seven criminal charges, two stemming from the charade he pulled for two years.

- Sex offender posed as boy

- Enrolled in schools

- Pleads guilty to seven charges

Authorities didn't find any victims of sexual abuse at the schools 30-year-old Neil Havens Rodreick attended in Arizona. But when his ruse was discovered in January 2007, they found an extensive collection of child pornography at his home.

Rodreick had originally faced 28 counts, but pleaded guilty to only a quarter of them Friday in Yavapai County Superior Court in northern Arizona, according to a plea agreement document obtained today.

Rodreick pleaded guilty to four counts of sexual exploitation of a minor stemming from the pornography, as well as one count each of failure to register as a sex offender, fraud and simple assault.