Artificial intelligence (AI) education is still in the exploratory stage for K-12 schools. There is a serious lack of studies that informed schools teachers about AI curriculum design. Accordingly, this paper presented an AI curriculum and examined whether the curriculum improves students' perceived AI knowledge, attitudes, and motivation towards AI, as well as caters to students with different genders and academic achievement. It involved 64 grade 8-9 students. Results show that in the AI curriculum, 1) the students' self-report indicated that they became more competent, developed more positive attitude and higher intrinsic motivation to learn AI, 2) there were insignificant differences between girl and boys, and 3) there were almost no significant differences between high and low achieving students.