What seems straightforward on paper might turn out to be complex in reality. This is a lesson often learned by educational designers when implementing variations of open-ended alternatives to traditional education and disappointedly reviewing the outcome. Based on observations of discouraging outcomes of alternative laboratory work in secondary and tertiary physics education we decided to approach the underlying cause of the problem. Framed in the theory of Didactical Situations in mathematics we adapt the concept of the didactical contract to the physics education context to locate aspects of the traditional laboratory learning environment that would lead to resistance from those involved if faced with alternatives. We conclude that both teachers and students lean heavily on a type of algorithm that ensures an appearance of having successfully completed the assigned tasks. This algorithmic didactical contract permeates through secondary education into university physics education. Our results allow for a better renegotiation of didactical contracts and thus for avoiding typical problems related to the implementation of alternative tasks. One might expect physics students to be special in their explicit interest in physics and thus plan educational activities accordingly. Based on our results, however, we find this an ill-advised strategy.