There are only 3 channels through which you can join IISER and these are - KVPY, JEE and last one is State and Central Boards Channel (SCB) channel. So there is no entrance but if you are going through SCB then you will have to appear in aptitude test.
To know more about IISER 2018, you can go through the below link-
IISER 2018
Good Luck!!!
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