Motivation for an action is determined by the expectation for success and subjective judgment on task values according to the expectancy-value theory. Task values, including intrinsic value, attainment value, utility value, and cost, influence and predict the students' engagement in learning activities and their choices in the future. This study validated the science, mathematics, and English task value scales using a longitudinal data. Data were collected from the 1234 middle school students of different school types, sizes, and districts in the Taipei metropolitan area. Confirmatory factor analysis, invariance, explanatory power, and higher order factor analysis were used to test the reliability and validity of the Chinese version across the three repeated annual collections of data and to develop a short version. The results showed that both the long and short task value scales are valid and reliable for measuring in-depth task values for different subjects, grades, and for long-term study. From seventh to ninth grade, the students' science task values decrease, the English task values are relatively stable, and the mathematics task values improve in Grade 8, but then decline in Grade 9. The implications of the scales for monitoring, intervening, and enhancing the students' task values are discussed.