Changed the code so it always address the user by first and last name.

<?php
$firstName ='Alena';
$lastName = 'Holligan';
$currentGrade = 11;
$finalAverage = 0.6;
$messageBody =' ';

if (!$firstName || !$lastName) {
  echo 'Please enter a student name';
} else {
  echo ('Dear $firstName $lastName, \n');
  } if ($currentGrade < 9 || $currentGrade > 12) {
  echo 'This is only for high school students. Please enter a grade between 9 and 12';
} else {
    if ($finalAverage < .70) {
      echo 'We look forward to seeing you at summer school, beginning July 1st!';
    } else {
      switch ($currentGrade) {
         case 9:
          $messageBody = 'Congratulations on completing your freshman year in High School! We’ll see you on September 1st for the start of your sophomore year!';
          break;
        case 10:
          $messageBody = 'Congratulations on completing your sophomore year in High School! We’ll see you on September 1st for the start of your junior year!';
          break;
        case 11:
          $messageBody = 'Congratulations on completing your junior year in High School! We’ll see you on September 1st for the start of your senior year!';
          break;
        case 12:
          $messageBody = 'Congratulations! You’ve graduated High School! Don’t forget to come back and visit.';
          break;
        default:
          $messageBody = 'Error: Grade level is not 9 -12.';
      }
    }
  echo ($messageBody);
}