Value is quite straightforward in my mind. It has several parts: a) students see value or a reason to learn the material without being told they must learn or get punished with poor grades; b) students learn to think about the what they learn and know in the context of how it affects others (or fits into a bigger picture), c) what students learn is challenging and engaging enough that it doesn’t feel like a dumb exercise to the student (e.g. a lab that can be looked up on Google that thousands of people have already done won’t fit this definition of valuable); and d) the process of learning creates confidence in the student and the process cultivates lifeworthy skills.
Not all learning will involve all 4 aspects of value, but the more the better!