In this example, the default="" attribute is set to default="2" and 2 refers to the second option in the list - State School , which is automatically highlighted when presented to a user. Defaults are zero indexed due to the way that Android processes select lists, therefors the 'Select' is zero and the options start from one.
This can also be applied in the same way to <radio> inputs.
Default options with <select> inputs
The following XML and screenshot demonstrate how to set two options selected by default.
<select ref="selectdemo" default="1,3">
<label>What facilities does the school have? Select none,one or more</label>