I have a teen mental health website, so it will be used by teens. In the T&Cs can I say, "You must be at least 13 years of age to use our website" or should I require parental consent?
It may be a good idea to include the age requirement in the T&Cs and in the body of any sign-up page. However, this will not be sufficient for some purposes (e.g. for consent to processing under data protection law). You should take proper advice on this from a suitable experienced lawyer, as the applicable rules are not always straightforward.