Same-scale Recruitment

WEST BENGAL SCHOOL SERVICE COMMISSION( briefly WBSSC) has published an advertisement for recruitment of GRADUATE AND POST-GRADUATE SCALE teachers. WBSSC give the opportunity to the Graduate in-service teachers to apply in the higher category Post-Graduate teacher scale. But none of the Post-Graduate teacher can apply in Graduate-teacher scale, nor any Graduate- teacher can apply to the same Graduate-teacher scale. Query : Is there any rule of SUPREME COURT/Other HIGH COURTS that 1. same category post cannot apply to the same post when he is in-service in that same post. 2.higher category post cannot apply in the lower category post in the same service (All the recruitments are direct recruitments, not departmental/promotional recruitment) Please provide some case details in brief. We want to move to division bench of CALCUTTA HIGH COURT and if necessary to the SUPREME COURT. Please Help