FEED THE BEAR

I am starting to work on webdesign with a group of 10 and 11 year olds. O usually use photoshop elements ot touch up pictures and the use the "save for the web" option to make images much smaller files - smaller in size and poorer in quality. How do I do this in paint.net - I have found the resize option but I haven't found how to reduce the quality of the picture - this reducing the size of the file for the web. I'd be so grateful if anyone can help me with this. Mark