Middle school grades won't follow on transcript to college so that's good.
On the lighter side without knowing you -
How were their grades during the course of the school year and in general through middle school. Struggling in math and providing a tutor is good. They are getting the extra help.
Without knowing your personal situation, it could be a sever case of spring fever, lazy, I can get away with this, I'm outta this school soon syndrome. Last quarter, fed up with middle school and simply don't care.
The teachers should have been sending emails to mom and/or dad as soon as a couple of assignments were missing. Quizzes and test scores not good? Again, blow the first two tests or quizzes, parents notified.
I'm not pinning anything on parents. Obviously by mid quarter some action should have been taken.
I'm hoping the twins have the I don't care I can get away with this syndrome and it's not the usual.
At 14 the grounding and punishment stuff works to a certain extent but serious behavior change doesn't work by time outs. Not at that age. Seems like a long summer ahead.
The military school threat sounds like a good idea to me. There's a lot more freedom in high school and they need to learn to be more disciplined in responsibility in getting their homework completed and handed in on time. The Tudor is a trade off. Parent is making the effort to get them extra help. Tell them YOU are shelling out extra money to help them and it's time for them to put in extra effort. Fair is fair. Nothing wrong with telling them they have to man up they are wasting your money and someone else's time.
Follow through in a loving fashion with military school threat Tell them you realize they would be much better off. You're concerned that high school will be too difficult and they probably won't like it because it's an extension of middle school with the same methods. They weren't doing the work required and nobody seemed to care at school and high school work is harder and less time management by teachers.
Even if youre not really sending them, instead of hard labor, seriously look at the private schools WITH THEM no matter how much they resist. Keep telling them it's a positive thing and bring them to every school within a reasonable proximity.
In other words, if they have the lazy I can get away with it spring syndrome, scare the crap out of them.
If I'm way off track here I apologize. Good advice for someone else maybe.