We formalise a thread-based concurrent language which makes resource control possible. Concurrency is based on a two-level model: threads are executed cooperatively when linked to a scheduler, and unlinked threads and schedulers are executed preemptively, under the control of the OS. We present a type and effect system to enforce a logical separation of the memory which ensures that (1) when running in preemptive mode, threads do not interfere with other threads; (2) threads linked to a scheduler do not interfere with threads linked to another scheduler. Thus, we get a concurrency model in which well-typed programs are free from data-races. The type system also insures that well-typed programs are bounded in memory and in their use of the CPU. Detection of termination of recursive functions and stratification of references in memory are techniques used to get these properties.