Am no expert in this area, yet your request surely deserves some response:
Wondering whether you are planning to buy the Macbook in Brazil before you go, or in the US when you get there.
(Eg: Seems Apple's warranty is only recognised in the country of purchase)
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If planning to buy in US ... you may want to read through the various replies in this discussion thread (link below)
Use of student discount in a different co… - Apple Community
and
Student Discount as a foreign student - Apple Community includes info. on US Payment policies
More info: Education Pricing and Student Discounts - Education - Apple
says: "Apple Education Pricing is available to current and newly accepted university students and their parents, as well as teachers and staff at all levels. Quantity limits apply".
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If purchasing in Brazil:
Talking to Apple: You can get support online from the big blue link in the article below:
Contact Apple for support and service - Apple Support (contact details worldwide)
For students: visit the Apple Store for Education or call 1–800–692–7753 (US).
Brazil contact:
0800-761-0880
Different countries, and even different stores within a country. may have their own student discount policies.
Apple's Store locator can help with store contact details worldwide: Apple Store - Find a Store - Apple
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If you use UNIDAYS: https://www.myunidays.com/partners/apple/view
Hope there is something helpful to you here!
All the best :-)