I have seniors, juniors, and sophomores and their parents in RE right now. This is a new school year with a new batch of freshmen and their parents, and also new students that have joined the upperclassmen. What is the best way to add them as constituents without being too tedious? I don't want to delete all of them and then re-import everyone, because I'd lose all gift information. Is there a way to import new people all without importing duplicates? Thanks!

No, you certainly don't want to delete everyone you have in your database.  

You will want to import the new constituent records. (Import is a function under administration.)  In import, one of the check boxes under options is "use duplicate criteria for new records." In your set up of RE, you or someone should have set some criteria to check for duplicates when adding a new record, like first 4 letters of last name the same, first 3 of first name.  Checking this box will check the names you are importing against those in RE.  (You can also run a report anytime to look for duplicates.)

Imports can be tricky to get formated and all the import ID set.  The RE training on import basics was very helpful for me. Good luck.

Ashley - Most of our education related clients that import student data 2x or more a year use Import-O-Matic, which has an advanced duplicate checker, but also allows you to bring in various types of data at the same time. http://www.omaticsoftware.com/Solutions/ImportOMaticAdvancedImporting.aspx . JoAnn- we also have two YMCA's using that for importing data from DAXKO and their website into RE.