It should work like said in my comment but maybe an even better way would be to use the acceptance filed-type that is build especially for that kind of checkboxes.
[acceptance term_and_conditions class:required] I can confirm I have read and accepted the <a href="http://www.your-domain.com/terms-page">Terms and Conditions</a>.[/acceptance]
In the contact form 7 edit page go to the tab additional settings and add:
acceptance_as_validation: on