In my recent post, Don't Prevent Students' Mistakes, Prepare for Them, I wrote that lesson planning should be more about anticipating students' errors and preparing to help them learn from those errors than trying to develop presentations that prevent all errors.

"Sounds good in theory," a teacher said when I made this point at a workshop. "But HOW do we anticipate and prepare to help students learn from their errors?"

"Most important," I replied, "you must do what I think of as teachers' homework--working through before class everything you'll be presenting, reviewing, or assigning during class."

Yes, everything--opening "Do Now," questions related to a book discussion or science lab, homework, etc. The likelihood of students learning to their potential from any activity often depends on you working through that activity ahead of time. It's only then that you're best able to anticipate students' mistakes and help them learn from their mistakes.

Recently, for example, a math teacher I was coaching asked students to find 0.5% of 1000. A tricky problem for students, but because the teacher had worked through it ahead of time and anticipated students' confusion (reading 0.5% as 50% or 5%), she was able to help alleviate their confusion without hesitation.

On the other hand, I've also been in classrooms--including mine as a harried new teacher--where teachers squandered one teachable moment after another because they hadn't done their homework. This typically shows up in two ways: 

• Inefficiency. Putting struggling students on hold as you work through problems or look something up online or in the teacher's edition is a waste of time--theirs and yours. Your focus when students are stuck should be on scaffolding their understanding, not getting up to speed on what they're doing.

• Inaccuracy. You're more likely to make mistakes when you discuss or demonstrate something in class without having given it careful, undivided attention before class. Worse yet, you risk students leaving class with misconceptions. I've seen this a lot in math classes where teachers zipped through problems they hadn't solved in advance. And I've seen it in other subjects too, like when a teacher told students the correct answer was "false" to a true-false question stating that President Bill Clinton had been impeached. (He made the common mistake of associating impeachment with conviction rather than accusation.)

Don't get me wrong. Even the best teachers make mistakes. But they don't make mistakes that can be prevented by proper preparation. And proper preparation involves more than being ready to introduce content. You must also be ready to help students as they interact with content.

A related point, which I first made in a post on differentiated instruction, is that you should spend less time presenting information and more time assessing and assisting students as they use information (similar in some ways to the flipped classroom approach). One benefit of this is that you'll be able to identify and clear up students' confusion during class rather than wait until you've reviewed their homework or other assignments after school.

And the less time you spend after school reviewing students' homework, the more time you have for doing your homework.