We take on students in counselling on a volunteer basis where we have a written contract with the universities/colleges and the volunteer student signs our standard volunteer agreement. 

However, there is nothing to prevent these volunteers from leaving at a moments notice, which makes it extremely difficult for us to plan and to deliver an excellent client service to those who need it most. Our HR department have told us that we can write a notice period in to our volunteer agreement but its not enforceable... Would it be best there is an expectation or should we try to include a length of service and notice period in the contract with the education units? 

Looking for help from other charities who take student placements, ideally, to see what they do.