surely the whole idea of teaching anyone is to expand their knowledge and understanding. If then one comes at a point where the student is not grasping some explaination because of a fundamental basic. Then the teacher needs to side step and explain that basic issue before moving on.
In this case m/s/s or m/s2. Surely then it is needed to take them off on another learning curve to grasp this little nettle before moving on.

What I don't grasp here is why would you be delivering a level of subject matter to people whom aren't quite up to the level of understanding.
If the've achieved NVQ2 then logically NVQ3 is the next level. The study material will be at a higher level , more in depth. Foundation knowledge should have been achieved at level 2. If understanding of powers etc is not in level 2 then level 3 is where it should be taught surely?