You need to master being utterly helpless to help him , no more offering suggestions or any other enabling comments.  These situations with DH get no where, so why bother?   

Did the teacher make a meeting with BM too? She definitely should as PS has two homes. If DH doesn't go it makes it look worse. He also needs to understand the teacher won't be thinking he's a bad parent, she's just wanting to do her job and communicate to the parents regarding a student struggling in her class. They won't be interested in pointing blame, they only want communication with a parent for a solution to help the student achieve their academic goals of passing. You probably already have told him but it's not about him, it's about his daughter. 

Wasn't there a recent conference about PowerSulk's attendance? (If I've mixed up posters I apologize.) If so, perhaps something was said at the conference that he did not tell you. He may be afraid to get called out for not following through with what he said in that conference.

Dear father of PowerSulk, avoiding a conference does not endear you to the teacher. She asked for the conference because she actually wants your child to pass this class. Your child not coming to math class is getting her further behind. No teacher minds catching up the truly ill, but all mind trying to catch up the frequently absent as with each absence they fall further behind. Attendance in math class is necessary for understanding as one skill builds upon the other. 

It looks as if another summer school summer is in the wings. 

Adding: Does DH realize it can be harder to join the military with a GED than with a high school diploma? 

https://www.operationmilitarykids.org/can-you-join-the-military-with-a-g....

Is SD physically fit enough to join the military? Looks like she will have to do a 2-mile run in under 19 minutes and she will have to meet strict weight requirements. Also there are health requirements they must meet and of course the psychological stress of boot camp.... Is this something SD is really interested in? If so she needs to start preparing now.

I'd stop giving parenting advice. He wants her to join military or circus, it's on him. The info about branches of military is readily available to everyone who's interested. Not classified. He could look it up. Like the rest of us. 
 

Same whth seeing a teacher. Up to him. Many neglectful parents  avoid teachers. He doesn't "only" has a child half the time. He HAS her half the time which she typically spends in her room and he is often with his boyfriend/best friend or fishing. So enough with blaming BM. It's up to him though if he meets teachers or not. 

 I am sure he hates teachers. He sounds like a typical person who thinks they are only after money and don't care about kids and are just out there to get these poor innocent parents. He sounds like one of those. "Wow, she cares"- is that his words/a quote? Like it's a surprise as they don't normally care. Rude. SMH 

disengage from parenting. Not your job to hold him accountable to parent HIS kids. This high level of involvement is yet to produce any positive result. It always backfires

“Hmm DH yeah that sounds like a lot, what do you plan to do?”  “My advice?  Oh well I guess whatever you decide to do would be the best course of action, I’m just here to support you.”

He’s a grown a$$ man who can figure out how to take care of himself daily…I think he can figure this out…will it be what you want?   Nope but that’s his piss poor parenting choice.

I've been in similar situations to yours. I wanted vindication so damn badly, but I finally had to accept that I was never going to get it. I went on strike. I never helped the SKs out again. I didn't help with HW, I stopped teaching SS piano and karate, I just stopped everything. 

I totally agree with JustK's advice to enjoy the Shadenfreude when it comes. And it will. However, when the Shadenfreude occurs, you still won't get that vindication from your DH. I so badly craved that from my DH but was so sorely disappointed when despite my SKs, especially SD proving me right and turning out to be a personality-disordered cow and DH going through a two-year profound depression over it, he still did not give me that vindication. I had to accept that I would never get that from him. However, I secretly thoroughly enjoyed the Shadenfreude. It was such a degree that I had to frequently prance off into the ensuite to lock the door and do my secret gloating twerk. Honestly, it was that delicious. The karma started several years ago and continues today. I have some really delicious Shadenfreude going on right now, but can't say on here because it'll identify me. 

The karma is already starting. The fact that your DH has to go in to talk to a teacher is karma. The fact that PowerSulk had to go to summer school or at least got assigned to it last year (sorry, I don't remember the details) is karma. So, just enjoy the fact that life is already playing out the fact that you were right and making efforts to do what was best for PS. Think of that and accept that as your vindication. We all know that neither of these events would have happened had you been able to stay engaged with PS's education. 

SD makes excuses not to go to school when she's in trouble.  DH resists meeting with the teacher cuz it might be uncomfortable.  I'm seeing a pattern here....

Clove, I dont think any of us are strong enough to turn around these long-engrained responses.  As you always say, disengagement is your friend.

Like others have said, schadenfreude really works, but in order to enjoy her failure, you have to get angry with her. You aren't, and you should be.

Clove.. honey.. you married a guy who is a poor parent.  period. 

He and his EX are both bad parents.

She is her parent's daughter.. they both seem to lack a lot of the qualities that would normally make people successful in life.  They both seem lazy and willing to blame everyone else for their problems.

BUT.. it's not YOUR issue to fix.  "I won't have a kid like that in my house"... sorry.. but yes you will.. because you married a guy who has that kid.. (a couple of them actually).. he has done a wonderful job of makng you think it's his Ex's fault.. when he has had ample opportunity to step in himself.. he let you do it.  I recall he is not even capable of learning how to access the online portal?  you give him too many excuses.. he is a mechanic.. supposedly has the ability to use equipment and fix complicated things.. he would do it if he thought it was important.. he doesn't.. he just wants to push it off.. he is lazy about parenting.. you can't change that.

Just found this article.  https://www.psychologytoday.com/us/blog/social-instincts/202302/3-ways-t...

Please look at and reread all the excellent advice you have been given on this site.  I’m saying this with all my heart.

You keep saying that you are going to disengage but you don't really.  You keep trying to control other people from a place of love in your heart, but it doesn't work.  

Block yourself from everything to do with your SDs.  Make sure that all alerts are going directly to your DH.

Then anytime anything comes up and your DH is talking about them, don't give him advice.  Learn a couple of platitudes and use them on him.  "Gosh, that sounds worrying, you'll have to think about what you are going to do"  "I'll support you in your decision"  "Hmmm" "Thanks for letting me know, now what about that concert/tv show/other activity."

If skid is messy, get your DH to clean it or pay for a cleaner.  Don't try to fix her.  Its futile.

If she gets a huge library fine, yawn and take 10x the amount your DH has to cover and put it in a savings account.

The only exception to this is to make is 1000% clear to him that no adult skids will be living in your home and mean it.

Many of the other posters have already given you version of this advice over the past while.  I hope you take it.  It will make your life calmer with less drama.

However, both of the nasty failed family spawn are the ones repeatedly choosing their behaviors.

You should by all means be angry with both of the nasty failed family spawn. 

And you should be mad at DH and TT.

That your DH continues to make excuses, justify,  gaslight you, and deflect on the  behavioral and character stench of both FF and PS is deserving of the disdain you hold them all in.

There will be repercussions. You have seen them. FF is living them. As is and will PS.  They are the product of their shit parents and it is likely that neither FF nor PS have the personal character or brains to avoid the shit outcome they are both experiencing at different points in the shit outcome continuum.  There is joy in consequences.  In cases like the one you are suffering through with your DH, TT, FF and PS, that is about the only joy there is in the SParent/blended family world. Until PS ages out from the CO and you and DH can escape to your own adventure with the 3 harpies screaching, crying, and gnashing their teeth as the fade into your pasts.

Time to just point out to DH that his failures are repeating. His cowardice is causing the same results for PS as they have already caused for FF.

Tell him that neither of his children will ever reside in your home after their 18th birthday because you will no longer allow yourself to be exposed to their toxic  presence.  It is okay to tell him that it breaks your heart to see his girls evolving as the shit that they are but that... is on him and on TT. 

Take care of you CLove.