Do you have access to a vinyl printer at the school? If so, customize your blank merchandise.
As you know, Spirit Box offers blank convenience items at wholesale price points. The advantage to ordering blank items is that there is generally no minimum quantities, and the price points tend to be lower then custom branded merch.
That said, customized products might be more appealing to your client base. If so, you can customize blanks...for cheap...using a vinyl or decal printer.
Many of you have access to this type of printer at your school. If not in your classroom, maybe somewhere else within the school. So ask around.
The Spirit Box team at Chanute High School, in Chanute Kansas, has a vinyl printer in their classroom, and have been adding their school logo to blank items like water bottles and bluetooth headphones, which they've had to reorder twice already this year.
Get creative with your team, obtain a pulse on what your target market (students and teachers) want, and offer that to them! It's a sure way to increase sales through your Spirit Box and school store.