It's actually 20% off the $50 sim only red plan, bringing it down to $40 postpaid per month for 18GB data, unlimited calls/texts - available in store for students, minimum term 12 months.
Some highlights from the same web page:
Students can also get 10% off postpaid Red plans valued at $40 and above (sim only and with handset)
Get 20% additional credit on each prepaid recharge.
Refer a mate to join a Vodafone Red plan and get $25 account credit each.
Is this a Sim Only Plan?