Joshua Lopez of Victorville was arrested this week by San Bernardino County sheriff's deputies after the victim's mother discovered the alleged relationship between Lopez and her child.
According to sheriff's officials, the two met socially outside of school before Lopez became the child's math tutor. The victim is not a student in the Adelanto School District.
Investigators said Lopez gave the child a cellphone so they could communicate freely during the relationship, which lasted for almost two years.
School officials said Lopez, 24, has been a substitute teacher at the Adelanto School District but not at any of the other districts in Victor Valley. The name of the school he taught at was not immediately released.
Lopez was arrested for lewd and lascivious acts with a child under the age of 14 and contact of a minor with the intent to commit a sexual offense. His arraignment is scheduled for Friday in Victorville.