I have more than 15 Category ,
And i have a custom taxonomy "classroom",
Is there any way to Create those categories automatically when i activate plugin?
When the plugin is activated, you can activate the custom taxonomy creation code.
You can create a scenario like this.
Plugin activated - Custom Taxonomy created - Category information is imported via the xml file you created before
You can export your taxonomy data (Tools - Export) and u have xml file.
And than follow this import code