The current study attempted to investigate the development of Arabic academic vocabulary knowledge among middle-school Arabic native speakers, taking into account the socioeconomic status of the Arab population in Israel. For this purpose, Arabic academic word list was developed, mapping the required academic words that are needed for adequate coping with informational texts as appearing in the different content areas text-books. Six-hundred Arabic speaking middle school pupils from the different areas in Israel, representing the different Arab subgroups: general Arab community, Druze and Bedouins, have participated in the current study. Two academic vocabulary tests, including receptive and productive academic vocabulary evaluation tests, were administrated to the students across the different age groups (7th, 8th and 9th). The results pointed to no significant difference between 7th and 9th grade in academic vocabulary knowledge. In contrast, significant difference was encountered between the different Arab sub-groups where the lowest scores were noted among the Bedouin sub-group, characterized by the lowest SES. When comparing receptive and productive academic vocabulary knowledge between 7th and 9th grade, the results pointed to improvement in receptive academic knowledge towards the end of middle school but not on the productive knowledge level. In addition, within participants' comparison indicated a gap between the pupils' receptive and productive vocabulary. The results are discussed in relation to the existing scientific literature and to its implication of both research and practice in the domain of Arabic literacy development.