CodePen

HTML

            
              <div>
	<input type="checkbox" id="get-last-quarter" onclick="toggle()" />
  <label for="last-quarter">Click here</label>
    <p id="last-quarter"></p>
</div>
<form action="events.php" method="post" id="schedule">
  <input type="checkbox" name="activity-1" id="activity-1" class="activity" value="1" />
  <input type="checkbox" name="activity-2" id="activity-2" class="activity" value="2" />
  <input type="checkbox" name="activity-3" id="activity-3" class="activity" value="3" />
  <input type="checkbox" name="activity-4" id="activity-4" class="activity" value="4" />
  <input type="checkbox" name="activity-5" id="activity-5" class="activity" value="5" />
  <input type="checkbox" name="activity-6" id="activity-6" class="activity" value="6" />
  <input type="checkbox" name="activity-7" id="activity-7" class="activity" value="7" />
</form>
            
          
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CSS

            
              
            
          
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JS

            
              function toggle() {

var checked = $("#get-last-quarter").prop('checked');

	if( checked ) {
			$(".activity").attr('checked', true);
	} else {
			$(".activity").attr('checked', false);
	}
}
            
          
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