JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/semantic-ui/2.2.11/semantic.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/semantic-ui/2.2.11/semantic.min.js"></script>
<select id="grade" name="grade" class="ui dropdown">
  <option value="">Grade</option>
  <option value="kinder">Kindergarten</option>
  <option value="g1">Grade 1</option>
  <option value="g2">Grade 2</option>
  <option value="g3">Grade 3</option>
  <option value="g4">Grade 4</option>
  <option value="g5">Grade 5</option>
  <option value="g6">Grade 6</option>
  <option value="g7">Grade 7</option>
  <option value="g8">Grade 8</option>
  <option value="g9">Grade 9</option>
  <option value="g10">Grade 10</option>
  <option value="g11">Grade 11</option>
  <option value="g12">Grade 12</option>
</select>

<select id="subject" name="subject" class="ui disabled dropdown">
  <option value="">Subject</option>
  <option value="kinder-esl" class="kinder">ESL</option>
  <option value="kinder-la" class="kinder">LA</option>
  <option value="kinder-health" class="kinder">Health</option>
  <option value="kinder-ict" class="kinder">ICT</option>
  <option value="kinder-math" class="kinder">Math</option>
  <option value="kinder-pe" class="kinder">PE</option>
  <option value="kinder-primary-grades" class="kinder">Primary Grades</option>
  <option value="kinder-science" class="kinder">Science</option>
  <option value="kinder-social-studies" class="kinder">Social Studies</option>
</select>

JavaScript

$(document).ready(function(){
  $('#grade').change(function(){
    $('#subject').removeClass('ui disabled dropdown').addClass('ui dropdown');
  });
});