[EDIT] コース選択画面へのヘッダーの追加と、ラジオボタンのcheckedを追加しました。

src/main/resources/templates/select_course.html

@@ -7,6 +7,7 @@
 <title>コース選択</title>
 </head>
 <body>
+	<div th:replace="~{header :: header}"></div>
 	
 	<h1>コース選択</h1>
 	
@@ -17,7 +18,7 @@
 		<div class="accordion" id="accordionExample">
 		  <div class="accordion-item" th:each="course:${courseList}">
 		    <h2 class="accordion-header d-flex align-items-center">
-			  <input type="radio" name="courseId" th:value="${course.courseId}" class="form-check-input ms-3 me-2">
+			  <input type="radio" name="courseId" th:value="${course.courseId}" th:checked="${course.courseId==currentCourseId}" class="form-check-input ms-3 me-2">
 		      <button class="accordion-button collapsed" type="button" data-bs-toggle="collapse" th:data-bs-target="'#collapse' + ${course.courseId}" aria-expanded="false" aria-controls="'collapse' + ${course.courseId}">
 				<span th:text="${course.courseName}"></span>
 		      </button>