If you'd like to quickly email parents and students (or just parents or just students), there are two easy ways to do this.
In PCR, click 'email' on the left column. At top of that screen it says 'Click here to send a new email'. Click on the word 'here' to open a page listing your students. At the top, you can choose which class or classes to email. In the list of students, choose which student families you want to email. Recall that checking the box at the top will choose all names beneath it. In the bottom right corner, under the dropdown "Select Multi-Action", choose to email parents, students or both. This will open a page for you to compose your email.
In FinalSite, choose the class you would like to email from your class options. Once directed to that class page, click 'Members'. This page lists the students in your class and has an option near the top to 'Bulk Email.' Clicking this button opens a pop up window that gives you options for emailing parents, students, or both. You can also choose to mail multiple classes simultaneously.