Simply put, learning progressions are planned directions to get learners to an end goal by using incremental steps in learning, sometimes known as scaffolding. Using the scaffolding technique, we can begin with simple learning outcomes, skills, or competencies then build on those step by step to achieve increasingly more complex sets of learning and induction until we reach the end goal desired.
Immediately, my mind goes to B.F. Skinner and his work on shaping. How does a circus performer get a bear to ride a bicycle (end goal)? Through the often-slow progression of reward through action, extinction, then reward again for increasingly complex interactions with the bicycle, then extinction again, and repeat the process. Being a behaviorist at heart I genuinely love shaping approaches to learning because they are generally small achievable steps that can lead to amazing behavioral changes over time. Problem is our learners are not bears on bicycles and learning outcomes do not equal behavioral outcomes. And more significantly, students are dramatically more complex creatures learning immensely more complex tasks (we also cannot give out chocolates every time a learner makes a correct response or keep the learning progressions a secret).

The activity in class made it abundantly clear that learning progressions need to be broad enough to encompass multiple types of learning styles and require a collaborative team of instructors to ensure the directions are being followed or modified and continuous over multiple grade levels. We also need to account for the various depths of learning that students may bring to class from previous experience or personal proficiency. Furthermore, accounting for all these variables while retaining engagement and motivation could be a major challenge. Never mind how to choose what skills or competencies are necessary to achieve the next level in the scaffold or how to translate those skills and competencies into definable learning outcomes with some measure of reliability. Factor in our commitment to inclusion, time constraints within a classroom, and variable pedagogical philosophies, and learning progressions become a legendary challenge.

Concerning the value, I believe learning progressions can have for learners, I accept such a challenge and off the top of my head, running parallel and integrated scaffolding may be an interesting way to accommodate levels of proficiency, teaching styles, and different heights of set scaffolding.