Welcome to science buddies!
Are your doing this excellent project?http://www.sciencebuddies.org/science-f ... p082.shtml
Your project has been successful; the crystals have just grown in the wrong place. They will continue to form on the sides of the glass as the water evaporates as crystals tend to form on any solid surface available. Can you take photographs and make conclusions with the results that you have?
It's possible that your string was too smooth and did not provide a suitable surface for crystals to form. Or, it's possible that there were particles of dust on the sides of the containers that were available for crystal formation. Was your saturated solutions perfectly clear, or were there any small undissolved particles that could have allowed crystals to start forming?
If you have time to repeat the experiment, do make sure that the containers are perfectly clean with no fingerprints or other particles; make sure the saturated solution is completely dissolved and clear, and definitely try using a string with a rougher surface. This should solve the problem. However, if you don't have time to repeat the experiment, you do have results that you can write up. Your explanation of why the crystals formed on the sides of the containers will make a good discussion section.
I hope this helps. Please let us know if you have more questions.