An employee wants to change his department from Administration/Operations to IT Department, How should He/She convince his/her manager?

It can be easy to convice them if your current department is compatible to the one you wish to join but if they aren't compatible like in this case; from admin/operations to ITdepartment, you will extra support to back up your urgument & proposal. You can put up a good urgument incase you provide evidence or proof of your capabilities that you can perform beyond reasonable doubt in that field you wish to join. Also if you have been previously in that field before or you have been currently studying classes or courses in relation to that field, you can be able to use that as evidence or proof that you are capable of performing highly in that field you wish to join.

Is not easy to convert a department whose responsibility seems that is not compatible with the proposed one.

What he / she must do is prepare a detailed report indicating who have skills from an administrative point of view and / or operations and those who are skillful in handling softwares and computing and thus redistributing into two units (adm. / operation and IT)

If he/she has skills and convincing certification for IT department.

I think it depends on your manager and depends on your working inefficiencies too. But there is choice that you can change your department. But before you going to change it, you have to qualify for the new post. May be you have qualify through presentation or any source which your management like it.

I am working in a School in IT from past four years. I want to go in Teaching Staff. My head office denied it. They said once you appointed for a post, you cannot change it. Until resign from the current post and join it again when the post will be vacant and if I fulfill their requirement for interviews and presentation.