I read on CC that you can ask schools for more money after you received the financial aid.
But does it include public schools? Or you can only do this with private schools?
You can ask any school anything you want.
in general, it is hard to ask Public ones for more money, especially for UC schools; but it does not hurt to ask
You can definitely ask but the chance is not high. Some public schools like UMich has a huge endowment and may have the resources for a student in a special situation. But usually that would be for someone with certain talent that they want. In other words, it is not likely they will give you more aid if you ask.
If you have some information that didn’t show up on the financial aid forms, it can be beneficial to ask. Job loss since paperwork was done, illness in the family resulting in large medical bills, etc.
My daughter goes to a public school and she did get more money after the initial award letter (her school has severall alumni awards of $2-5K). The FA office also might be able to direct you to some department scholarships or to some small local ones (banks, civic clubs). Look on the web page, but also call and ask. It might help if you had some facts that could be important (medical bills, job loss or loss of income because of a weather problem in your area). You might get something like more work study or a suggestion for a cheaper housing option.