Like in real life, there are some things in this Academy, that are not allowed.
For example, some Deck types:
-Burn
-Mill
-FTK
-Stall
-Exodia
None of these decks are allowed.
If you use it for a test, you will be retested.
If you use it for a duel, your opponent wins automatically.
There are many other Decks. There's no reason for you to use a Deck from the "Ban List".