Seniority shall be determined by establishing the beginning date of the first full-time contract for continuous full-time professional services for Community College District V and continuous professional services for the Everett school district prior to July 1967. Continuous service shall include leaves of absence, professional leaves, and periods of layoffs. The longest term of employment as thus established shall be considered the highest level of seniority. In instances where faculty members have the same contract beginning date of full-time professional service, seniority shall be determined as described in the collective bargaining agreement.