I homeschool so I pop on and off all through the day. I'll be watching for you. I won't check until late in the morning (around 10am CST), after I get the kids started in school.
I quick way you can check for the straight of grain is to give your squares a tug. Choose only one, because you won't be able to use the square after you do this. Hold it on the right and left and give a tug and "feel" the stretch. Repeat for the top and bottom. There should be a little give (one side will give more than the other). Now do the same thing holding two opposite corners. There is where your biggest stretch should be. If they were cut properly that is the bias of the fabric and will have the most stretch. Use that square as a practice square after you do this test because you will most likely pulled it "out of square" and it won't be perfect measurements anymore.
Have fun!
Shelly