How to Add Student_ID to Devise Confirmation Email To Be Emailed to User

How to Add Student_ID to Devise Confirmation Email To Be Emailed to User

I have a rails application where a user needs its student_id to access
some features.
The default devise confirmation email is this
<p>Welcome <%= @email %>!</p>
<p>You can confirm your account email through the link below:</p>
<p><%= link_to 'Confirm my account', confirmation_url(@resource,
:confirmation_token => @resource.confirmation_token) %></p>
I want to know where the
<%= @email %>
is from ?
I tried adding
<p>Your student id is <%= @student_id %> ! Please don't forget ! </p>
but it did not work.
I have this in my routes
devise_for :students
then a link_to to the new_student_registration path in
application.html.erb and then a simple_form in that registration view
under devise, after a user signs up the user will get a confirmation email
sent by sendgrid.
My question is won't that particular student's record be exposed during
the sequence from above? and hence that is where the
<%= @email %> comes from?
why can't I pass in the student id to be emailed as well?