We present the design and prototype implementation of the scheduling component in ARTCOP (architecture transparent control of parallelism), a novel run-time environment (RTE) for parallel execution of high-level languages. A key feature of ARTCOP is its support for deep process and memory hierarchies, shown in the scheduler by supporting light-weight threads. To realise a system with easily exchangeable components, the system defines a micro-kernel, providing basic infrastructure, such as garbage collection. All complex RTE operations, including the handling of parallelism, are implemented at a separate system level. By choosing Concurrent Haskell as high-level system language, we obtain a prototype in the form of an executable specification that is easier to maintain and more flexible than conventional RTEs. We demonstrate the flexibility of this approach by presenting implementations of a scheduler for light-weight threads in ARTCOP, based on GHC Version 6.6. © Springer-Verlag Berlin Heidelberg 2008.