Garliccalamari I can see where you are coming from and it's not fundamentally a bad idea - unfortunately the maths just doesn't work.
Currently children are in school for 5.5 hours a day for 190 days a year which is 1045 hours of education per year.
If school holidays were just 28 weekdays a year to match a standard office worker's annual leave, the remaining weekdays available for education are 233.
1045 hours divided over 233 days of education is 4.5 hours per day. So you would be asking teachers to give up 43 days of holiday in exchange for just one hour a day less workload.
The additional work that teachers do over and above school hours is typically at least 4 hours a day so the teachers would still be exhausted and working into the evening, but would just have lost the recovery time.
Kids would also lose out - they need the holidays to rest their brains a bit and run around in the sunshine.
The solution as pp said is really to employ more teachers so that each teacher only has 4 hours teaching and 3 hours preparation/marking each day, then we wouldn't have so many qualified and talented teachers leaving the profession in droves, broken. That would require more taxes of course.