According to studies by Hattie and Marzano, various forms of feedback (teacher -> student, student -> teacher, peer -> peer) have proven especially effective for improving students’ learning performance. However, there is a question of how to organize feedback of this kind, especially when class size may be significantly larger than 20 students.
In his book Evidence-Based Teaching, Geoff Petty  proposes the possibility of using mini-whiteboards.
Mini-whiteboards are laminated DIN A4 pages that are also available in DIN A3 format. They can be written on using a felt pen or fine whiteboard marker. Corrections can be made using a microfiber cloth. Mini-whiteboards of this kind can be reused indefinitely, just like their larger cousins.
- Rapid feedback about the latest state of understanding
Using the mini-whiteboards, the teacher can generate feedback about the current state of understanding from the entire class. This can take the form of a pretest at the start of the class hour, verification of an interim goal during an ongoing lesson, or as a final summary at the end of a teaching unit. Students can quickly respond to a question from the teacher and show their answer to the teacher by holding up the mini-whiteboard. Besides providing rapid information for the teacher, it is also possible to stimulate a classroom discussion about the current teaching material in this way: the students will take interest in what their fellow students have written and thus engage with responses that might differ from their own.
Examples for their application:
- Language teaching: questions about vocabulary/grammar ….
- Mathematics: drawing graphs, solving math problems, preparing outlines, ….
- Physics: drawing circuit/experiment diagrams, physical calculations, developing solution strategies, …
- Feedback about in-depth understanding
In the process of learning, new content is incorporated into the previously existing cognitive maps that we carry inside our brains (see: The development of mental models). It is possible to visualize these connections through mind-maps and other graphical organizational structures. As students become familiar with the use of such tools, they can graphically represent the connections within a particular subject area on the mini-whiteboard. The teacher can see at a glance any misconnections that may have been made.
If students have yet to master the use of graphical organization structures, the teacher can begin by creating a knowledge map (mind map, etc.) on the board in collaboration with the students. Next, the students can be asked to transfer this map from memory onto their own mini-whiteboards.
- Peer-Feedback with the Mini-Whiteboard
According to studies by Hattie  and Marzano , peer feedback has unparalleled value. Mini-whiteboards are especially well suited for initiating feedback processes between the students.
If, for example, one considers the procedures described in Item 2 for developing graphical knowledge maps, the students can exchange their work with each other and mutually amplify and improve it. A helpful option is for the collaborating students to use different-colored markers. Afterwards, they can explain their enhancements to one another.
It is also possible to use peer processes to develop solution strategies for more complex problems with the mini-whiteboards. To do this, each student starts out with some time to reflect on a solution for a given problem. Then, a set number of students (at most 12 per group) line up, paired in two rows. On a signal from the teacher, each pair has two minutes to explain their proposed solutions to each other. Next, the rows change position (similar to speed-dating) and the game starts over again. Each time they explain their approach, the students have to reflect about it again while at the same time, receiving new input for their solution from their fellow students. In this way, a group solution for the problem can be generated.
 Petty, G., Evidence-Based Teaching (2009), 2. Auflage Nelson-Thornes
 Hattie, J. (2009) Visible Learning. Routledge
 Marzano, R. et al. (2001), Classroom Instruction that Works, ASCD, USA