Could you give some examples of what you mean by the "formative assessments" you said you build in to your planning? And I'm curious as to how you go about "anticipating student challenges"...how and what kind of challenges?
Wiggins and Mctighe (2005) posit (and I would agree) that assessments include standardized exams, in-class exams, quizzes, academic prompts, performance tasks, and informal discussions. Informal discussions might occur around homework, student portfolios, Socratic Method, among others. Broadly speaking, all assessments can be broken down into two categories: formative and summative.
Summative assessments are often associated with standardized tests; they are defined as any assessment that measures learning. They measure what knowledge and skill sets the student has acquired in the past. When teachers assign grades, they usually (but not always) are applying summative assessments.
Formative assessments set out to promote learning, and in contrast to summative assessments are more prospective or forward-looking. The most common example are informal discussions with students that are intended to help them achieve something they could not do before. When teachers are in class, they constantly observe students who are struggling and thus make adjustments to either their teaching practice and/or they suggest to learners to make adjustments to their learning tactics. This is an example of formative assessment...we are assessing and tweaking the educational design in order to help students learn more effectively, efficiently, and through higher engagement.
I mentioned before that exams were "usually" considered summative assessment - but they don't have to be. Dynamic assessment is a term used to describe how teachers use the results from student exams, for example (which are typically summative assessments) as a type of formative assessment. Teachers build a lesson (i.e., a learning experience) around common problems reflected in the results that came from the results.
So, formative assessment techniqually can be any type of assessment, but it is what you do with the test, exam, informal discussion, etc. that matter. The purpose of formative assessments is to create better learning experiences; the purpose of summative assessment is to measure learning. In formal education, both are important, but my philosolphy leans on having more formative assessment than summative. As in the case with dynamic assessment, anything can be turned into formative assessment.
As for anticipating student challenges, there are two perspectives to consider: the novice practitioner and the expert practitioner. The novice teacher perhaps will lack at being able to anticipate certain student challenges. So, what I would suggest is to record or share classroom experiences as often as possible and inquire about what others are doing. One's personal learning network (PLN) can come in handy when using social media to share experiences with others in this regard. Simply asking questions to others often can create a discourse around working towards a possible solution - make learning transparent. Then, complement this with what the literature (research) states.
The expert practitioner perhaps can anticipate more problems that students are likely to face. But since each group of students is unique, being a reflective practitioner and sharing one's experiences with others (like in the case of the novice) can also be beneficial.
For me, being a reflective practitioner and sharing my experiences with others has helped me cultivate my own PLN in a way that helps me become better as an educator. I often reach out to my PLN when it comes to student challenges. These challenges are often linguistic, technological, and managerial when it comes to when, where, and how they set out to achieve the objectives of the class. I receive a lot of good information via my PLN and this has helped me learn how to be more in-tune with my students. For me it's just paying attention to the types of feedback that I repeatedly give (i.e., formative and summative assessments) and then reflecting on and sharing what I learn as often as possible. This is the approach I currently take.