OP I’m glad you’ve calmed down, perfectly fine and good to rant.
Everyone’s said on here basically the same that there is no right answer and there’s absolutely no way to please and satisfy everyone. The playing field is very out of balance right now (and tbh always has been in education in many ways) and you’re not alone.
I second phoning the school. I’m a teacher, I’ve spoken to all the parents and had reactions of all extremes. Give them a ring (it may be that you arrange a time for teacher to call you back depending on who you get through to you, or just email them direct and arrange a time) and just calmly and politely express your concerns and your situation. You won’t be the first. Ask what you should prioritise. Ask what you can do instead.
Also agree with the level thing - I’m sending out worksheets (I don’t do this many worksheets at all normally) at different levels and have started sending out work titled “optional extra / extension” to ease the pressure on parents and satisfy the ones who want more.
A 5 and a 6 year old - so either Year R and 1 or 1 and 2? I teach reception, my personal recommendations, should you be struggling with completing the actual set work:
At that age, reading! Ten minutes of reading each day so that there is always exposure. Oxford Owls has a free section with the school reading books on.
Top Marks is a very good website to use on a tablet for maths games - I realise leaving children unattended for long is an issue obviously but if they are the type who can sit on an iPad for half an hour and leave you be, explore some of the maths games on here. At least then if you’re not able to do the set maths for example, they’ve done some (in a hidden way)
Word flash cards around the house that they’re working on in phonics or spelling or whatever - constant exposure and quickly pointing them out and running through them a few times a day (literally just “what’s this word again? Was! Well done off you go”
Ultimately, the literacy and maths. If you can’t do it all, these subjects one a day will be of the most benefit.
Just to add on the phone calls and work, it’s another rock / hard place situation. I’ve phoned parents who have basically said (mostly very emotionally) what you said, they haven’t had time and it’s too much, so I’ve told them what to prioritise and given suggestions based on the child. Likewise I’ve also been asked to leave them alone! Some parents have said it’s too much work, some have said they’re done by 11am and want more! We’ve been instructed to “check in” but don’t pressure parents for work, but also keep tabs! There’s no winning answer here. The plan for next term is major catch up and consolidation.....