theme/child

There’s a lot of info on support pages about using child themes to make edits. I’ve set one up with a style-sheet. It’s activated and uses @import url(“../twentyeleven/style.css”) to load the parent theme. So far so good. But I can’t find any info about how to REMOVE code, rather than to add code.

For example, I’ve removed the search form: <?php get_search_form(); ?> from the header but had to do that in the parent theme because I couldn’t figure out how you do that in the child theme? Is the idea to add php functions and then add something to invalidate the function?