A brilliant class

What's the definition of a brilliant lesson?

One where 100% of the students are engaged and doing something 100% of the time.  One where you know exactly what each student has understood at each stage of the lesson.

I have the good fortune to currently be observing two teachers who demonstrate this concept beautifully.

One class I observed involved a jigsaw reading where each group read and made sure they understood one section of the reading, then regrouped so that every student had to explain their section to the others.  The teacher monitored the entire time and every student ended up with a thorough understanding of the text.
Another was a math class where the kids were practicing mental math.  In the first class, the teacher would give the students problems such as "what's 7+6+5-3?"  and 5 or 6 kids would call out the answer, which meant the others didn't have a chance.  However, the next time I saw the lesson, the kids were all sitting on the carpet with little pieces of paper and pencils.  They were only allowed to write the final answer and then hold it up to see if it was right.  EVERY child participated. 

This is what school should be!