My youngest is your DD's twin in some respects.
She at least has got much better at remembering lunch, money for pizza days, and bringing back books to the library. Taking a daily shower is still something we fight about, daily. She has trouble transitioning from comfy existence in her room to taking off her clothes and getting in under the water. However, once in, she spends an hour there. From my previous experience of another DD with trouble transitioning, this phase passes, but DD4 is taking more time than the other one did getting over herself.
When it comes to revealing the smallest piece of information about homework or upcoming tests or how she did in a test she has already taken, forget it. I am used to the occasional rudeness and tetchiness of 11-14 year olds as the older ones all had it to some extent, but not about school performance. The others all wanted to do well in school and felt bad when they saw a B on a paper or test. DD4 thinks avoiding an F is an achievement.
She has been tested along the way for learning difficulties/SNs (blowing off school expectations is nothing new) but as the school specialist said to me when going over her results, 'the little minx scored in the high nineties in every area'. They do not have much to offer for a student who could do the work if she put her mind to it, but just won't.
It's possible she is a 'late bloomer' as some have suggested, and will settle down and take to work once she turns a bit older. Right now, I am inclined to think she is actually just plain lazy and stubborn, and has arrived at a place where she can balance her desire to waste time/be entertained against how bad she feels about the Fs and 'could do better' comments in reports. My mum blames it on her early development and menarche at 11, but mum (bless her heart) tends to see the arrival of periods as a cataclysm in a young woman's life, so I am inclined to take this wisdom with a grain of salt.
As to consequences -- she is currently assigned to 'homework room' twice a week after school to catch up on Spanish she had completely blown off and redo half-assed work she scribbled in class while pretending to be too cool to work, and she will stay there until her grade rises to a C. I am going to ask the teacher to keep her there until she is getting a B, just to show her how little work will get you a B, and that just a little more attention to detail, could get you an A. So far she has been a little ashamed about the homework room, but mostly she has been resentful, and determined to play down the importance of raising her grade. When the homework room experience is over, she will have to do a detention for all the missed work too, plus several instances of eye-rolling and daydreaming in class. TBH I think the teacher should have had her do the detention first but heyho.
I want her to feel the desire to work and to get good grades, not to work because I have taken various items from her or restricted access to them. However, I am coming to the conclusion that the tablet exH got her for Christmas needs to be taken and time on it rationed. Phone use in her room is already forbidden. I am also considering a carrot in the form of weekly payment for improvements such as telling me when she has a test coming up, evidence of studying (including letting me quiz her on the material), evidence of correcting mistakes in maths that will earn her half points for exercises where she had some wrong, and telling me what homework she has plus showing me completed work. I am not interested in her actual grades here, for now. What I want to see is good habits and a willing attitude. I didn't have to do this with anyone else (maybe DS had a touch of it, but he at least took tests seriously because he felt some shame about bumping along with C minuses). It's the attitude, unique to her in the family, that what I am asking is completely 'shocking', 'intrusive', and 'unreasonable' (all words she has used, at 12.5) that gets my goat. I am the one who is paying the fecking school fees.
One thing that worked to some degree with DD4 last summer was paying her weekly for chores I asked her to do on a daily basis while I was out at work. She was to empty the dishwasher, load it up, and set it running when full. The kitchen floor was to be swept, and the bathroom sink swished with window cleaner. On Fridays I had her go through the fridge and pantry and also check the bathroom for supplies, and start a shopping list. If something wasn't done one day I docked her for the day. I gave her a floating list of things that needed to be done that she could get on with any time she chose, with each item worth the daily amount. These chores were a bit more yukky -- cleaning the loo, emptying all the waste paper baskets and the bathroom bin and taking it all out, digging out the litter box, clearing off the coffee table, dusting thoroughly, etc. The hope was that she would develop the skill of managing time. While she did pretty well and seemed to bask in my approval when I praised her for her efforts, she never once maximised her weekly earning potential.
Next summer I am putting her in volleyball camp and also putting her name down for 'volunteer' work in the local library, which should get her up and about, and on top of that I will have the chore regimen in place, going by the motto that the more you expect a teenager to accomplish in a day the more they will get accomplished. She is tall and likes volleyball, and likes the library too (more accurately, she likes the fizzy drink machine in the library and this is where she spends her money). I will dock money for showers not taken, on top of chores not done -- I will not pay extra for showers taken.
When I cut off the supply of sugary snacks, DD4 learned to bake brownies. Sometimes I come home from work to find 3/4 of a pan of 16 eaten. Full marks for initiative I suppose. She also developed a fondness for the library, but that had an upside in the form of a fixation with historical fiction that resulted in an encyclopedic knowledge of the Tudor and Stuart periods.
Items like changing out of uniform I never bothered about. TBH, I didn't care whether any of the older ones lived in their uniforms, or the order in which they got their work done, snacks consumed, or entertainment/relaxation accomplished. They all managed their time whatever way they wanted and I reminded them about chores if they hadn't done something they had agreed to do, like sorting out clothes that needed a wash or stuff they had grown out of. My theory with the others was that they knew what I expected of them and it was up to them to bring their priorities into accord with that, and they did not fight me on the issue of expectations so it worked. It is the shrugging of the shoulders about school and homework that has me so worried about DD4. That plus the very irritated response to reminders.