Got the solution,

Printed the report by giving a href to the button like this,

<a t-attf-href="'/report/pdf/account.report_invoice/%s' % i.id">
    <button type="button" class="btn btn-primary btn-md o_website_form_send">Print Invoice</button>
</a>

In the i.id i have the id of the invoice.
This is the format,
report/type_of_the_report/module_name.template_name/id

To print the report from the  controller,

@http.route('/school/card', methods=['POST', 'GET'], csrf=False, type='http', auth="user", website=True)
def print_id(self, **kw):
    student_id = kw['stud_id']
    if student_id:
        pdf = request.env['report'].sudo().get_pdf([student_id], 'module_name.report_name', data=None)
        pdfhttpheaders = [('Content-Type', 'application/pdf'), ('Content-Length', len(pdf))]
        return request.make_response(pdf, headers=pdfhttpheaders)
    else:
        return request.redirect('/')