You should be able to find all student names within your Gmail directory. Alternatively, enter the name of the student or member of staff you want to find and hit Search.
To locate an individual type their full name (or initials) and second name, for example:
Joe Bloggs or J Bloggs
Up to 30 entries will be displayed. If you search for a common name, eg Smith, then the name you want isn't likely to be one of those listed. Try to give as much detail as you can to narrow down the search.