Big problem or not?

[transientChris]

I will have a 12th grader and a ninth grader next year. Due to my older dd's medical issues in 9th grade, she hasn't done world history as a high schooler. Normally I would do WH in 9th grade and I plan to do that with my 9th grader. In terms of science, my 12th grader will be doing physics but then so will my ninth grader. She is totally bored with life science and biology and I think physics is what she should do. Mainly I am having the ninth grader do this because I expect her to do AP Physics later on. ALthough I will have the older do world lit, I will have the younger do an intro to lit class. THe older is much better in English. They also won't be at the same place in math since the 12th grader will be doing pre-cal and maybe stat and the younger will be doing Alg2 and Geometry. NOw here is the rub- my two girls don't get along all that well. The younger is a typical prepubescent hormonal irritating child and doesn't particularly get along with any family member right about now. She is very perfectionistic while her older sister is extremely competitive.
I don't plan to teach them at the same time and the older will be relying more on lectures and the younger on texts. However, any tests I design will be mostly the same for physics though for world history I will give more essay tests to the older while using more multiple choice for the younger. Because of this and the more difficult lectures that will be the basis for the older's class, she will have her class designated as honors.
They have completely different personalities and interests. So older will probably like the history more and younger will like the physics more. Am I setting myself up for catastrophe or do you think this will work? Any suggestions?

[In The Great White North]

My senior and my 9th grader both did US History with The Last Best Hope this year. The 7th grader did US History too but with different materials. It was fine. All they actually did together was watch the movies.

It all depends on how much you want to do together and how well they work together.

[Pam L in Mid Tenn]

I had a similar problem when my girls were late elementary to middle school. It ended up being "easier" for me to NOT try and teach them together at all. Since then they've had different courses every year. We've used many of the same books, just not at the same time. But that makes more work for me. But we don't have the competition or fights about whose turn it is to use the book. LOL

I have done some writing lessons all together. Only the lessons. I edit/grade privately.

What is more important to you? Less teaching/grading / planning?? OR Less girl arguments in the house?

[Nan in Mass]

I taught mine together (4 years apart) for most subjects until the older one graduated. My older one isn't competative, though. It worked very well. I expected more writing from the older one, and one was reading Spielvogel while the other was doing Kingfisher (for example). It worked very well. The discussions were better, it was more fun to do experiments together, and it was easier for me.
-Nan

[Ruth in Canada]

They use different materials, and I don't make any attempt to teach them together. But it means that I don't have to get my head around two different sciences, and they do overhear me working with each other.