No leave of absence shall be granted under this article to any employee for study purposes who has not rendered service to the district for at least seven consecutive years, or for retraining purposes who has not rendered service to the district for at least three consecutive years preceding the granting of the leave, and no more than one such leave of absence shall be granted in each seven- or three-year period, respectively. The governing board, or personnel commission in merit system districts, may prescribe standards of service which shall entitle the employee to the leave of absence.

Any leave of absence granted under this article shall not be deemed a break in service for any purpose, except that such leave shall not be included as service in computing service for the granting of any subsequent leave under this article.