diff --git a/management/src/index.css b/management/src/index.css
index 66c2238..4028697 100644
--- a/management/src/index.css
+++ b/management/src/index.css
@@ -5197,6 +5197,14 @@ input:checked + .slider:before {
   color: #ffffff;
 }
 
+.grid-proctor-container {
+  display: flex;
+  flex-direction: column;
+  flex: 1;
+  min-height: 0;
+  overflow-y: auto;
+}
+
 .grid-proctor-layout {
   /* Columns configured inline */
   transition: all 0.3s ease;
diff --git a/server/internal/websocket/websocket.go b/server/internal/websocket/websocket.go
index 48af6a5..984e198 100644
--- a/server/internal/websocket/websocket.go
+++ b/server/internal/websocket/websocket.go
@@ -23,8 +23,16 @@ type SocketClient struct {
 	StaffID   uint
 	Role      string // "student" | "teacher"
 	Addr      string
+	writeMu   sync.Mutex
 }
 
+func (c *SocketClient) WriteJSON(v any) error {
+	c.writeMu.Lock()
+	defer c.writeMu.Unlock()
+	return c.Conn.WriteJSON(v)
+}
+
+
 type WsHub struct {
 	mu              sync.RWMutex
 	students        map[int64]*SocketClient
@@ -54,7 +62,7 @@ func (h *WsHub) PushExamToStudent(studentRkID int64, data map[string]any) {
 	if !ok || client == nil {
 		return
 	}
-	_ = client.Conn.WriteJSON(SocketMsg{Event: "exam:paper-sent", Data: data})
+	_ = client.WriteJSON(SocketMsg{Event: "exam:paper-sent", Data: data})
 }
 
 func (h *WsHub) PushChatToStudent(studentRkID int64, data map[string]any) {
@@ -64,7 +72,7 @@ func (h *WsHub) PushChatToStudent(studentRkID int64, data map[string]any) {
 	if !ok || client == nil {
 		return
 	}
-	_ = client.Conn.WriteJSON(SocketMsg{Event: "chat:message", Data: data})
+	_ = client.WriteJSON(SocketMsg{Event: "chat:message", Data: data})
 }
 
 func (h *WsHub) PushChatToStaff(staffID uint, data map[string]any) {
@@ -77,7 +85,7 @@ func (h *WsHub) PushChatToStaff(staffID uint, data map[string]any) {
 	defer h.mu.RUnlock()
 	for _, t := range h.teachers {
 		if t != nil && t.Role == "teacher" {
-			_ = t.Conn.WriteJSON(msg)
+			_ = t.WriteJSON(msg)
 		}
 	}
 }
@@ -107,8 +115,8 @@ func (h *WsHub) Register(c *SocketClient) {
 		h.students[c.StudentID] = c
 		log.Printf("[WS] Student %d registered (Address: %s, Class: %d)", c.StudentID, c.Addr, c.ClassID)
 		if subs, exists := h.subscribers[c.StudentID]; exists && len(subs) > 0 {
-			_ = c.Conn.WriteJSON(SocketMsg{Event: "start_screenshot_stream"})
-			_ = c.Conn.WriteJSON(SocketMsg{Event: "start_webcam_stream"})
+			_ = c.WriteJSON(SocketMsg{Event: "start_screenshot_stream"})
+			_ = c.WriteJSON(SocketMsg{Event: "start_webcam_stream"})
 			log.Printf("[WS] Student %d has active subscribers. Sent start stream commands.", c.StudentID)
 		}
 	} else if c.Role == "teacher" {
@@ -132,7 +140,7 @@ func (h *WsHub) Unregister(c *SocketClient) {
 		if teachers, exists := h.subscribers[c.StudentID]; exists {
 			for _, tAddr := range teachers {
 				if t, found := h.teachers[tAddr]; found {
-					_ = t.Conn.WriteJSON(SocketMsg{
+					_ = t.WriteJSON(SocketMsg{
 						Event: "teacher:stream-stopped",
 						Data:  map[string]any{"studentId": c.StudentID},
 					})
@@ -170,8 +178,8 @@ func (h *WsHub) Unregister(c *SocketClient) {
 				delete(h.subscribers, sID)
 				// Nếu không còn ai xem học sinh này, gửi lệnh tắt camera/screen cho client học sinh
 				if student, exists := h.students[sID]; exists {
-					_ = student.Conn.WriteJSON(SocketMsg{Event: "stop_screenshot_stream"})
-					_ = student.Conn.WriteJSON(SocketMsg{Event: "stop_webcam_stream"})
+					_ = student.WriteJSON(SocketMsg{Event: "stop_screenshot_stream"})
+					_ = student.WriteJSON(SocketMsg{Event: "stop_webcam_stream"})
 				}
 			} else {
 				h.subscribers[sID] = newList
@@ -201,8 +209,8 @@ func (h *WsHub) Subscribe(teacherAddr string, studentID int64) {
 
 	// Phát lệnh cho máy học sinh bật stream (nếu học sinh đang online)
 	if student, exists := h.students[studentID]; exists {
-		_ = student.Conn.WriteJSON(SocketMsg{Event: "start_screenshot_stream"})
-		_ = student.Conn.WriteJSON(SocketMsg{Event: "start_webcam_stream"})
+		_ = student.WriteJSON(SocketMsg{Event: "start_screenshot_stream"})
+		_ = student.WriteJSON(SocketMsg{Event: "start_webcam_stream"})
 	}
 }
 
@@ -229,8 +237,8 @@ func (h *WsHub) Unsubscribe(teacherAddr string, studentID int64) {
 
 		// Báo học sinh tắt camera & screen stream để tiết kiệm mạng và CPU
 		if student, exists := h.students[studentID]; exists {
-			_ = student.Conn.WriteJSON(SocketMsg{Event: "stop_screenshot_stream"})
-			_ = student.Conn.WriteJSON(SocketMsg{Event: "stop_webcam_stream"})
+			_ = student.WriteJSON(SocketMsg{Event: "stop_screenshot_stream"})
+			_ = student.WriteJSON(SocketMsg{Event: "stop_webcam_stream"})
 		}
 	} else {
 		h.subscribers[studentID] = newList
@@ -262,7 +270,7 @@ func (h *WsHub) RelayFrame(studentID int64, event string, data map[string]any) {
 
 	for _, addr := range teachersList {
 		if t, found := h.teachers[addr]; found {
-			_ = t.Conn.WriteJSON(msg)
+			_ = t.WriteJSON(msg)
 		}
 	}
 }
diff --git a/server/server.exe b/server/server.exe
index 7c7e053..c4ab49b 100644
Binary files a/server/server.exe and b/server/server.exe differ