I assume your bylaws define the procedure for amending the bylaws. So yes - if the bylaws prohibit something it is always possible that the board could follow the appropriate procedures to remove that prohibition, as long as it doesn't violate IRS provisions.
As for the articles of incorporation - as long as the charitable purpose of the organization remains charitable, then yes, they can be amended. Each state has its own rules as to the procedure for amending the articles of incorporation. So if the original articles and/or by-laws limit the scope of the charity to supporting one particular school, to expand that scope would require an amendment to either the articles of incorporation or the by-laws (or both), which would have to be approved by the board.
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