I' m newbie in odoo and have just created my first module with scaffold. I edit controller.py with

@http.route('/first_odoo_module/first_odoo_module/', auth='public') def index(self, **kw):

         return http.request.render('first_odoo_module.index', { 'teachers' : ['one', 'two', 'three'], })

and  in templates.xml  : <template id="index"> <ul> <li t-foreach="teachers" t-as="teachers"> <t t-esc="teacher"/> </li> </ul> </template>.
then run : "odoo.py -d Test -u first_oddo_module " and got error
QWebTemplateNotFound: External ID not found in the system: first_odoo_module.index
How can I resolve this ?