Already a handful of "how does this compare...?" postings but the standard for a systems-programming scheme is scsh, a find abstraction layer over POSIX dating from the nineties.
I think maybe there is a different interpretation of the words "systems programming"?
I took it to mean a scheme used for developing close to the hardware programs, where as maybe others are taking it to mean a language which can be used to write common scripts and tools used by Systems Engineers.
Close to the hardware can also be done with scheme and indeed has been done in the past. Look at all the smartcards, running a JVM. For scheme, it just requires some engineering effort and there is not much demand for it. Btw, there is picobit(https://github.com/stamourv/picobit) which can be run on micro-controllers.
PreScheme serves the same sort of role within the Scheme48 ecosystem. It's been a while since I've looked at Scheme48, but if I remember right, the VM is written in PreScheme, which is usually compiled down to either C or machine code. However... you can also run PreScheme code within Scheme48, so that it's possible to test/update the VM semantics without actually compiling down to C for each dev cycle.
scsh is purely interpreted and interfaces well with user-level programs but was being put forth as a systems-programming tool - while this works for some definitions of systems programming, it doesn't for others, and it is this distinction that the parent was pointing out.
I took it to mean a scheme used for developing close to the hardware programs, where as maybe others are taking it to mean a language which can be used to write common scripts and tools used by Systems Engineers.