Focus on the email subject - it must be clear and make the advantage stand out. For example "
Don't miss the SALE up to 70%" or "LAST CALL | Last day of sales" or even "ALL costumes at -50%! Now we're thinking 
"Start the body of the email by explaining the student data offer (e.g. -30% on all items from last season)
Describe the promotion in detail
Give a preview of the discounted products in photos (inserting original price and discounted price). Tip: use the photos you take for social media and insert them in emails. Save time, make communication more uniform.
Insert the Call To Action (the call to action) in a nice button. The call to action can be: come to the store, buy now (if you have an e-commerce), place your order.
To give you an example, here's how many.
Instagram and Facebook to communicate sales
Once you have programmed SMS, RCS, WhatsApp and email, you are halfway there.