California Code, Education Code - EDC § 44909

(a)(1) The governing board of a school district may employ persons possessing an appropriate credential as certificated employees in programs and projects to perform services conducted under contract with public or private agencies, or categorically funded projects that are not required by federal or state statutes. The terms and conditions under which such persons are employed shall be mutually agreed upon by the employee and the governing board of the school district and the agreement shall be reduced to writing. The expected end date of employment, the source of funding, and the nature of the categorically funded program or project shall also be included in this writing.

(2) Service pursuant to this section shall not be included in computing the service required as a prerequisite to attainment of, or eligibility to, classification as a permanent employee unless (A) the person has served pursuant to this section for at least 75 percent of the number of days the regular schools of the school district by which the person is employed are maintained, and (B) the person is subsequently employed as a probationary employee in a position requiring certification qualifications. Such persons may be employed for periods that are less than a full school year and may be terminated at the expiration of the contract or specially funded project without regard to other requirements of this code respecting the termination of probationary or permanent employees other than Section 44918.