Hello @GDYO ,
Anti-spam and privacy compliance wouldn't really allow for emails to be structured quite like this in our mass-marketing email system. That said, there's some possible workarounds and roundabout ways of achieving this.
Having individual lists for each student and their parents' addresses. Then, you'd send a copy of the email where you've specifically typed out details - i.e. "Hello Student Name and Parents," to the corresponding list for each parent+student combo.
Utilizing custom fields for the parents to include verbiage like "Parents of [Student Name]." Then, you'd have two separate emails to send out. One email will be sent to a students-only list with a standard greeting tag. Then, you'd send a copy of the email with the custom field instead for the greeting - i.e. Hello {Parents of Student Name} - that you send to a parents-only list. Effectively, you always have two copies of each email, one that's been edited to greet the students by name, and the other to specifically greet the parents by calling them "parents of student."