The visa issuance is sponsored by the company to whom you are visiting. Once you leave that company (Flight School in your case) the visa is then null and void and when you want to return to the US to a different flight school, you will need to start the visa process again.
Also - the visa expiry date doesn't mean anything - it is the CBP Officer at the port of entry who will determine how long you can stay.
The visa itself simply gets you onto a plane to the US - not how long you can stay.
This is all documented on the USCIS website if you go look.