I will soon begin earning an income in Europe and paying off school loans in the U.S. Any way to do this without paying an extra exchange fee?
You will always pay exchange fees when you exchange currency. The minimum would the the price arbitrage - the difference between the buy and sell prices.
Shop around and check where the exchange rate is the most favorable for you and go there. Don't just look for "no fees" signs because the fees are still charged, through a less favorable exchange rate. Nothing is free, and currency exchange services included.
You would probably get better rates with wire transfers than with checks or exchanging cash.