What is formative assessment in class?
Formative assessment is checking in order to adjust, not to grade. It happens during the lesson, right after the explanation, while you can still act on what you see: the class practises together and with support, and you check that everyone is with you before they work on their own.
The difference with raised hands is that everyone answers. A structure gives every pupil a turn, so you do not hear the three fastest but see who does not have it yet.
Which structure checks what?
To retrieve the previous lesson or the explanation just given, use Taking Turns, On time or One by one: everyone names one thing, and whoever has nothing left passes. Knowledge Quiz, Shuffle & Pick and Movement Quiz check with questions: in Movement Quiz pupils quiz each other and find a new partner on the signal.
To practise with a classmate's feedback, use Pair Coach or Flashcards: one solves or answers, the other watches and may only ask questions. In Numbered Minds and Think, Write & Share everyone thinks alone first, then the group confers, and every member must be able to explain the answer.
What to watch for
Decide beforehand what you will do with what you see. If three quarters have it, the class moves on and you take the rest aside. If half do not, you explain again, differently: formative assessment without a consequence is just a quiz.
Keep the questions small and concrete: one concept, one step of a calculation, one rule. Big open questions belong in processing, not here. Mini whiteboards or paper work too; the structure makes sure everyone takes part and the time is on the board.