When shopping for supplies for the upcoming school year, try to only buy new things if you really need it. You should try to reuse old supplies from previous school years if possible. For example, instead of buying a new backpack every year, reuse the same one and only get a new one when it is falling apart.
Don't buy more than you need. Estimate how many supplies you will need and only buy that amount.
Look into brands that sell eco-friendly products. For example, pens or pencils that are biodegradable.