Most modern mail clients identify links in plain text messages. I suggest you to start with a simple solution - you don't need Perl for that. Make an alias for your list of students in your .mailrc, create the body of the message with a plain text editor say in /home/rio/students-reminder, and then put a mail invocation in your crontab.

If this isn't satisfactory, CPAN is your friend. I suggest take a look at Email::MIME::CreateHTML. There is a simple example right in the documentation.