In order to get help you are probably going to need to provide more information. Some of the questions that I have are:
- Is the survey set as visible to students?
- Which survey are you trying to use?
- Can you state the settings of the survey? (you could take a screenshot and upload it)
- What version of Moodle are you using? (If you are using Moodle 1.7 or newer there may be issues with changed permissions???)