Question

if you do not attend school you cannot join Oscar (use unless)​

Answer 1

Unless you do not attend school , you

cannot join Oscar .

Answer 2

The correct form of the statement using the word 'unless' will be:

Unless you attend school, you cannot join Oscar.

The word 'unless' means 'except if'. It is used as a conjunction to describe an event that is not true or valid( a conditional type of statement).

The clause that comes right after 'unless', is a subordinate clause and it needs a main clause to give the sentence a complete meaning.