Crossword Wizard is a nice application that will allow you to create crosswords for your students very easily. You will be able to create Standard crosswords (from a word list) and Dictionary crosswords (from a selected word range and number of letters or family). The program also comes with a great number of templates to use, but these are only available in the registered version. The program comes with many word lists divided by category (fruit, family, bikes, animals, etc.) that you can easily edit according to your liking or needs. You can also type your own clues or get definitions from the built-in dictionary, and give your crossword any shape you want.
The program allows you to add images as a background. You can use the ones that come with the program or add your own. All your puzzles can be saved and printed, and you can customize the title, write instructions, select exactly what you wish to print (clues, border, solution, footer, etc), select the position of the clues, and add answer hints. The application offers a very simple user interface that anyone can understand, especially if you use the templates.
All in all, if you are looking for a comprehensive application to create nice as well as challenging crosswords for your students, Crossword Wizard may be a good choice.