Opinion of Advocate General Kokott delivered on 12 March 2019.#Daniel Ustariz Aróstegui v Departamento de Educación del Gobierno de Navarra.#Request for a preliminary ruling from the Juzgado Contencioso-Administrativo No 1 de Pamplona.#Reference for a preliminary ruling – Social policy – Directive 1999/70/CE – Framework agreement on fixed-term work concluded by ETUC, UNICE and CEEP – Clause 4(1) – Principle of non-discrimination – Public sector education – National provision granting additional remuneration only to teachers employed for an indefinite duration as established public officials – Exclusion of teachers employed under a fixed-term contract governed by public law – Concept of ‘objective grounds’ – Characteristics inherent in the status of established public officials.#Case C-72/18.