ASA is designed so that you pass the test if you read and digest the materials. It is in your and the schools best interest that you pass and continue on. I have heard of only two people that did not pass, and it was because they decided not to take the test because they decided that sailing was not for them.....for whatever reason.
As you go up in numbers you should continue to pass as long as you are interested. The most difficult is Navigation, but even that can be easily passed with work.
Have fun and you will do just fine.