I vary depending on level but it is possible and I do do it sometimes. For example at one school each grade is broken into A, B, and C levels. There I prepare anywhere from 5 to 6 lessons across 9 classes. For example, 2B and 1A might get the same lesson while 3A gets a more advanced lesson that no other class could handle and 1C gets a very, very low level lesson that would be too easy for any other class.

But at another school I teach almost the same lesson across all 3 grades with only minor changes or swapping out of an activity or two. It is definitely possible and I do it depending on the school/level of my students. It has never been an issue for any of my co-teachers.

I often use the same lesson as a blueprint across three grades.  I'll go more in depth with my more advanced class (not the oldest class, actually), but the content will be pretty much the same between all three grades.  We don't work from the textbook, and this gives me a framework from within I can be flexible and improvise when parts of a lesson go over poorly.

I teach at middle schools and high schools (four schools total, different kids every day) so I get quite a lot of mileage out of my lesson plans.  I'll make different lesson plans for middle and high, but I can often use the lessons between schools in addition to between grades.  It's convenient, and it also means that I find out what works where.  My middle school boys love competitions, so I'll make sure to include an active component in their lessons, but my middle school girls are often too shy to compete head to head with one another, so I can tweak a competitive component into a cooperative one which they enjoy much more.

Ultimately, it's up to you and your co-teacher.  My co-teachers all like this approach, because it means that we can be more present with our kids and focus our time and energy on making a really strong framework rather than on making many lessons.

Thanks for the input everyone. Greatly appreciated!

I'm in the same boat as you, aklim. My kids were just recently divided into beginner/intermediate/advanced. I wasn't asked to prepare modified lessons for each though (thank God). Not sure how your sanity is able to survive that!

Anyways, I appreciate your responses guys. Thanks again.

I occasionally teach the same lesson (adjusted for level) across different grades but they tend to be more cultural lessons, like when I do something for Halloween or Thanksgiving, etc.

I used to do one lesson for all my classes from time to time and vary the difficulty depending on the grade

on the plus side of it, there was less prep time and you became an absolute expert on the content of the lesson by the time you are finished.

on the minus side, it can get VERY monotonous to teach 22 lessons a week with exactly the same subject, you will have nightmares about the lesson when you sleep.

I asked at on my first day if it's OK, and my Co-t's said it is. Of course I only teach high school once a week but it makes it easier to plan one lesson instead of 3.

I do something like this at my rural middle school. In total I have five classes--1st grade 2 classes, 2nd grade 2 classes, 3rd grade 1 class (but split into high and low level).

I don't teach from the textbook, so I have lots of freedom, which is great. MY main school has me teach from an awful text and every week I struggle to make their horrible example sentences relevant and interesting.

What I do is make a topic or theme for the week and create similar lessons. For grade 1 and 2 I do the exact same lesson, but I'll either simplify the vocab or give them sheets with glossaries for Korean to English words. My school is really low level so I have to keep it as simple as possible. My 3rd grade Low class get the same lesson as the 2nd graders. For 3rd grade high level, I make a spin-off or "elevated" lesson.

For example, this week I'm doing a "BFF" lesson. Last week we did a "personality test", so this week we're going to talk about what qualities we want in our best friends. They'll describe their best friend's qualities in a written story and talk about it to the class. At the end we'll play a KABOOM paper strips game with relevant sentences from the lesson. Writing and Speaking focus, done.

My 3rd grade High class is getting the same lesson, but rather than describing friends it's about dating. "My Ideal Partner": describe your "specs" and what you expect your partner to look like. I have a list of common Korean "dating specs" so we'll see if anyone strays from the norm. Then I'll teach them about "Dealbreakers" as their slang of the day. After I've called them all on their shallowness (it's bound to happen) I'm going to give groups a letter written to a fake newspaper column asking for relationship advice. They'll read the short letter and have to come up with good advice, then share with the class.

The idea is to save yourself time by using the same ideas/activities/themes and just tweaking them for each level. Last semester I was putting tons of work in, but now lesson planning is a breeze because I know the shortcuts and I'm used to the way it works. I used to do 3 completely original topics and lessons for each grade and was tearing my hair out making them perfect. This way I can just change the wording and content ever so slightly. I asked my co-teachers if it was okay and they said that I was "really a real teacher wow!", hahaha!

I also had success going off the middle school lesson boards. For my grade 1 I went to elementary grade 6 and drew inspiration from there. For my high-level grade 3 I went to the high school boards and found some amazing ideas. After that it was just a few edits to make it appropriate and I was done!

Continuity is also a good thing. Right now I'm doing themes. The first 2 weeks were travel (vacations; postcards) and this is the Personality theme. Coming up I have media/technology, sports, cooking, the Future, culture (Canada and others), etc. I do 2-3 lessons within each theme so I can build on similar vocabulary and really get it to stick. one-off lessons, unless they're stellar, tend not to stick. Last semester I did a "home" lesson. We started with rooms, furniture; then we did house design and chores. They got into it because they were stoked that they remembered everything form last week.

Good luck! sorry for this long post.

I did this last year. One lesson across two schools with levels adjusted.
That means this year I had to make a fresh batch of lessons instead of being able to reuse my old ones from last year.

I asked to teach from the textbook this year. Saves me a big a headache on thinking what I should teach this week.

Interesting... I was under the impression that teaching from the textbook was the bigger headache. Are you the exception or is that the general consensus among foreign teachers?

As someone who has to plan up to 10 different classes per week without any textbook or guidelines whatsoever, I think going by a textbook would be a huge timesaver. Maybe it's not as much freedom, but too much freedom takes a lot of work. Not to mention that maybe half of my classes are multi-level.

Hitting the nail on the head here.

Hmm... I guess it depends on your particular situation then eh? I'd imagine that creating ten lessons from scratch would be rather annoying indeed... But in the case of someone who only has to prepare one lesson from scratch (as I hope to do), it shouldn't be too time-consuming, right?

I also forgot to mention in my original post that I've been asked to teach only the speaking parts of the textbook... So I'm in the same boat as philby1985. I think that has probably been a big factor in terms of the difficulties I've been having putting 45-minute lessons together.

So, I think in my case... At least I hope... Prepping one lesson from scratch will be a lot less stressful and a more enjoyable experience overall.