An investigation has been launched into allegations that a high school teacher in California has been rewarding students with "Bible cookies" and offering extra credit to those who copied out Bible verses.

The complaint against teacher John Alameda, filed by a student at New Vision High School, says he is in "clear violation of the US constitution".

The student is being supported by Americans United. Legal fellow John McGinnis sent a letter to the local Superintendent, Jason Messer, setting out the allegations.

"We have received a complaint that New Vision High School teacher John Alameda is using his official position to promote an after-school Bible club," McGinnis wrote.

"We understand that Mr Alameda not only sponsors the club but also shares his Christian beliefs during school hours and frequently encourages his students to attend the club's meetings. Furthermore, he offers extra credit for copying Bible verses and gives students "Bible Cookies" as a reward for completing class assignments.

"We write to inform you that these actions violate the Establishment Clause of the First Amendment to the US Constitution. We ask that you take steps to ensure that Mr Alameda complies with constitutional requirements."

McGinnis then clarifies that US law prohibits teachers from sharing their faith with students during school hours "and incorporating religious content into the curriculum for extra credit and as rewards".

"It is well established that the [Establishment] Clause prohibits school employees from using their official positions to promote religious activities or religious perspectives to students in any manner," he finishes.

The Manteca Unified School District is yet to respond fully to the complaint, but released the following statement: "While respecting the diversity and beliefs of our community. MUSD is dedicated to ensure the separation of church and state as prescribed by law."

MUSD has not responded to a request for comment at the time of publication.