The bottom line is:
You will NOT get any more school days and you will not get any more hours per school day, until and unless:
1) Tuition is raised a commensurate amount to the number of additional hours and days you are seeking
and
2) Rebbeim, Morahs, and teachers salaries are raised a commensurate amount of money to the addional hours and off-days you seek to add.
Without both these conditions stringently applied across the board, you cannot and never will get the change you seek. Complaining that tuition is too unbearably high and cannot go higher may (or may not) be true. But even if it is true, without an equivelent increase of tuition — for everyone including those who cannot afford it — you simply will NOT get more school hours.
P.S. Girl schools have no Sunday hours, so you cannot do a trade-off between Sunday and Friday. And if you do it for boys schools, you’ll end up with your boys and girls having different school schedules on Friday.