If your instructor expects you to use opamps, then use them as comparators.

Following is a circuit which uses comparators to do what what you want, but you could just as easily substitute opamps. 

I'll post it now so you can study it, and I'll add a circuit description sometime later today if I can get to it.

in the meantime, [here's an LTspice .asc file][1] you can use to simulate the circuit if you want to play around with it  


[![enter image description here][2]][2]


  [1]: https://www.dropbox.com/s/by7w4zf9c6fk38i/Window%20comparator%202.asc?dl=0
  [2]: https://i.sstatic.net/cmPNX.png