Best time to apply

A

Hello,
i want to apply for a Masters in business in France, some of the programs i want to apply to, give the application with good GMAT score a competitive advantage and my test is in 12- March, but i wouldn't get a good score by than ( my current score is terrible) so i thought i would postponed the test for 5 weeks to be in 16-April, but people always says the soonest the better to guarantee a place, so do you think i should submit in March with a bad GMAT score or study and get a good GMAT and submit in April? and is April a late time to apply? is really my chances decrease with time ?

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