A one-parameter scaling of the magnetization curves of the high-temperature superconductor Tl-Ba-Ca-Cu-O causes all data points in the irreversible regime to collapse into a single curve M=H*f±(H/H*). The scaling field H* is inversely proportional to temperature and f+ and f− are the scaling functions for fields H above and below H*, respectively. The results are explained in terms of the Bean model. We argue that these features are common to all type-II superconductors.