A. All persons who become employees after March 1, 1952, shall be members of the retirement system, except for the following persons:
1. Any person who elects not to participate as provided in this chapter, or who elected not to participate in the abolished system.
2. Any person who becomes an employee and who elects to remain a member of a local pension system where such election is allowed by state law.
3. Any member of a local system who through promotion achieves a position bringing him within the definition of a teacher if he elects within sixty days, with the concurrence of his employer, to remain a member of the local system.
B. No person shall hold more than one membership in the retirement system at any one time with respect to any of the benefits provided under this title. Any person employed in more than one position resulting in membership shall elect one position on which his membership shall be based by written notification thereof to the Board.