The approximate amount an individual will get back at tax time is $69 from federal, $14 from state. The total is $83.
In the end, you actually give $167 and your school gets $500.
Most of these companies named also have a "Dollars for Doers" Program. After an employee has volunteered a designated amount of hours to the school, the company gives the school varying amounts of cash to match the employee donation of time. This may also include time spent at Parent Group meetings.
Source: Minnesota Council of Foundation's website, Internal Revenue Service website, Taxcut software, company websites. Not to be construed as tax advice.