Student tickets are reserved for whomever can prove they are actively studying or holds a valid student card. In some cases student tickets may actually cost more than normal tickets, as the price is set by the seller listing them.
What is a MEIA ticket?
If the tickets you want to purchase say "MEIA" it means they are tickets for residents in Brazil and you must fulfil the requirement of being a STUDENT, SENIOR, GOVERNMENT TEACHER, DISABLED, etc. Proof of meeting one of these requirements must be presented at the box office of the event.