I am starting my 18th year of teaching, which means I have overseen the ordering of over 50 different show shirts in my career. Life became easier once I started using Google Forms, no more lost sheets of paper. I simple copy the embed code or if your website is a Google Site just click insert and show shirt available to order.
You can also add more questions, if you needed to do an order for dance shoes and/or make-up kits.
Another use for Google Forms creating a contact list for you productions.
You can also customize your confirmation message. For this, one I reminded them the day the money was due.
Here is links that can help you learn how to use forms.
Please feel free to contact me if you need help. firstname.lastname@example.org