Recruiting high-quality physics teachers for low-socioeconomic status (SES) schools is essential for ensuring equity but is challenging globally. China launched a four-year program to meet the challenge by providing free education and stipends and promising a career position to attract high-performance secondary graduates, while using a contract to constrain participants to serve 10 years as K-12 science, technology, engineering, and mathematics teachers, with the first two years in low-SES rural schools. This program had recruited more than 101?000 preservice teachers in all academic areas, and more than 90% went to teach in low-SES rural schools. In this paper, we clustered participant physics teachers according to their motivation to serve low-SES schools and commented that the use of the "carrot and stick" policy has both positive and negative effects. On one side, the preservice teachers who had higher motivation for serving low-SES communities increased their motivation significantly during the four-year professional learning; on the other side, a portion of teachers who had lower initial motivation failed to develop adequate motivation. Even though the carrot and stick model seems to achieve its established goal, we argue that the "carrot-stick" policy may need adjustment and that the implications from this preservice teacher policy are useful for developing policies in other countries.