I have to say, it seems as though this rule within your forum has been abused or at the very least has been completely taken out of context. What is technically considered plagiarism would be those questions from their books or tests (not that many would be able to actually ask a test problem online during an exam). However, it seems as though your community has taken this to a completely different level to include any "work" in connection with a school, whether that be for a school project or otherwise. From a philanthropic perspective, this is definitely not the way of a collaborative engineering society. There are several national middle-school, high-school, and even collegiate-level engineering competitions where there is a wealth of knowledge that could be shared in order to assist such engineering students grasp a concept and apply it rather than turn them away because of "forum rules and etiquette". There is something to be learned by the engineer as well through teaching, mentoring, and guiding. In my opinion, only a forum that is ill-equipped to handle such questions would turn-down students seeking assistance for such projects. While this is your forum and you can obviously set the rules any way you want....there are hundreds of other forums out there where prospective engineers are gaining familiarity, loyalty, and making connections within because such strict limitations don't exist.