Depends on whether you are put in a SEO1 post or not. Every job vacancy in a school/division is a "post", and each post has an establishment grade based on the job desc/title/level of responsibilities. If the estab grade for your post is SEO1, then you are eligible to be promoted to SEO1.

It's more clear-cut in schools because it's mapped to a fixed set of job titles, but in HQ it can be hard to tell from job title alone because of the wide variation.