If Python had followed the TeachScheme! strategy, you could sandbox the student programs by running the module in the language that they are supposed to use. The languages are well-specified so that students can't write malicious code. Period. All code that could be malicious comes from a TeachPack, written by you. The technology to make that work is to support modules that are written in different languages and link them together (also dynamically) as if they had been written in one language. The rest is a mixture of threads, resource containers, and externally controlled event spaces, but I suspect that Python has these kinds of things. Works like a charm for 1000's of students, assuming you have a big enough machine. -- Matthias