@Meltedcheese2 I feel for you, and also acknowledge your understanding of the school situation! My DD (now in Y9) was a bit more fortunate in that her class wasn't full of challenging children, but she was a bit forgotten at times as she was ahead of most of the pack, and we were planning for her to sit the 11 plus so wanted to make sure she was covering all bases in the early years.
It sounds as though your DD's school is doing a good job, considering the challenges, but of course it would be better for your DD to have a bit more attention and for you to feel confident she is being nurtured and challenged appropriately at school.
I agree with the majority that say that a little bit of support at home will make a big difference. I appreciate time is at a premium as you work full time, but it is quite easy to add value at primary level if your DD is receptive.
I note your DD is already GD at reading, but nevertheless, IMO reading is the easiest thing to do with her. You may already be doing this already, but reading together for a few minutes every day makes such a difference. Take it in turns to read passages so you can model good reading to her - using appropriate expressions, using different voices for the different characters etc. Stop and discuss new words, and look them up in the dictionary (ideally a paper one!) and discuss alternative word options and discuss why the author may have chosen that word. Ask her questions - how does that passage make her feel? What does she think might happen next, and why? Try to use a range of authors and include some non-fiction. Even if she is already a capable reader, it will add so much value if you can develop her vocabulary and inference skills, and it can be fun too!
Also, be grammar police when you're out and about. My DD can spot a missing or misplaced apostrophe anywhere - café menus or posters etc.
We found maths a bit harder to enhance, but only because DD is more literary minded and enjoyed the word games but could spot a sly maths question a mile off! Yours might be more open to this though! We found some good ideas and games on Maths Playground an Nrich, and we had a subscription to IXL for a while, but you can do 10 questions per day for free. You can find out the National Curriculum maths requirements for Y4 and could consider resorting to workbooks if you feel these might help. We favoured GCP books when we started 11 plus workbooks in Y5 so the maths/English ones for Y4 may be worth a look. If your DD still has maths tutoring, you may not need this.
If your DD is bored in lessons, or she is not understanding some of the content but isn't able to ask questions, you could approach the school as @DUsername has suggested (ie making it specific.)
Also, on the subject of your DD getting the message that it doesn't matter if you work hard or not, she's at a good age to start understanding that that's not the case. You can explain to her that she is not working hard to please a teacher - she is working hard to develop her skills so she can do well at school and in her future career. It's her journey and her opportunity in life and she needs to make the most of it.
You might want to encourage her to start asking the teacher for help, or asking for harder work. My DD started doing this in Y1 and if it is done politely, it does get them noticed eventually - and it is an important life skill.