diff --git a/app/api/announcements/route.ts b/app/api/announcements/route.ts
index c922561..7c7f7c7 100644
--- a/app/api/announcements/route.ts
+++ b/app/api/announcements/route.ts
@@ -7,7 +7,7 @@ import { z } from 'zod'
 const AnnouncementSchema = z.object({
   title: z.string().min(1),
   content: z.string().min(1),
-  audience: z.string().optional(),
+  audience: z.string().optional().default('all'),
   category: z.enum(['academic', 'events', 'admin', 'general']).optional(),
   pinned: z.boolean().optional(),
 })
diff --git a/app/api/grades/[id]/route.ts b/app/api/grades/[id]/route.ts
index 0141f63..ebc1a24 100644
--- a/app/api/grades/[id]/route.ts
+++ b/app/api/grades/[id]/route.ts
@@ -35,7 +35,7 @@ export async function PUT(req: NextRequest, ctx: { params: Promise<{ id: string
 
     await connectDB()
     const grade = await Grade.findOneAndUpdate(
-      { _id: id },
+      { _id: id, teacherId: userId },
       sanitizedBody,
       { new: true }
     )
@@ -56,12 +56,15 @@ export async function DELETE(_req: NextRequest, ctx: { params: Promise<{ id: str
   try {
     const { id } = await ctx.params
     await connectDB()
-    const deleted = await Grade.findOneAndDelete({ _id: id })
-    
+    const deleted = await Grade.findOneAndDelete({
+      _id: id,
+      teacherId: userId
+    })
+
     if (!deleted) {
       return NextResponse.json({ error: 'Grade not found' }, { status: 404 })
     }
-    
+
     return NextResponse.json({ success: true })
   } catch (error) {
     if (error instanceof Error) {
diff --git a/app/api/grades/route.ts b/app/api/grades/route.ts
index b9da63d..643d668 100644
--- a/app/api/grades/route.ts
+++ b/app/api/grades/route.ts
@@ -3,6 +3,7 @@ import { NextRequest, NextResponse } from 'next/server'
 import { connectDB } from '@/lib/mongodb'
 import { Grade } from '@/models/Grade'
 import { z } from 'zod'
+import mongoose from 'mongoose'
 
 const GradeSchema = z.object({
   studentId: z.string().min(1),
@@ -41,7 +42,11 @@ export async function GET(req: NextRequest) {
     const subject = searchParams.get('subject')
 
     const query: Record<string, unknown> = { teacherId: userId }
-    if (studentId) query.studentId = studentId
+
+    if (studentId && mongoose.Types.ObjectId.isValid(studentId)) {
+      query.studentId = new mongoose.Types.ObjectId(studentId)
+    }
+
     if (subject) query.subject = subject
 
     const grades = await Grade.find(query).sort({ createdAt: -1 }).lean()
@@ -58,22 +63,22 @@ export async function POST(req: NextRequest) {
 
   try {
     await connectDB()
-    
+
     let body
     try {
       body = await req.json()
     } catch {
       return NextResponse.json({ error: 'Invalid JSON in request body' }, { status: 400 })
     }
-    
+
     const parsed = GradeSchema.safeParse(body)
     if (!parsed.success) return NextResponse.json({ error: parsed.error.flatten() }, { status: 400 })
 
     const data = parsed.data
     const max = data.maxMarks!
     const term = data.term ?? 'Term 1'
-    
-    const grade = Grade.findOneAndUpdate(
+
+    const grade = await Grade.findOneAndUpdate(
       { teacherId: userId, studentId: data.studentId, subject: data.subject, term },
       { $set: { ...data, term, teacherId: userId, grade: calcGrade(data.marks, max) } },
       { upsert: true, new: true }
diff --git a/app/api/profile/route.ts b/app/api/profile/route.ts
index a3d98bf..89fc2e3 100644
--- a/app/api/profile/route.ts
+++ b/app/api/profile/route.ts
@@ -22,7 +22,7 @@ export async function GET(req: NextRequest) {
       const clerkUser = await currentUser()
       const created = await Teacher.create({
         clerkId: userId,
-        name: clerkUser?.fullName ?? '',
+        name: clerkUser?.fullName?.trim() || clerkUser?.firstName?.trim() || "Unknown User",
         email: clerkUser?.emailAddresses[0]?.emailAddress ?? '',
         department: '',
         subjects: [],
diff --git a/app/api/students/[id]/route.ts b/app/api/students/[id]/route.ts
index 2eaaf93..aaf01b4 100644
--- a/app/api/students/[id]/route.ts
+++ b/app/api/students/[id]/route.ts
@@ -35,7 +35,7 @@ export async function PUT(req: NextRequest, ctx: { params: Promise<{ id: string
 
     await connectDB()
     const student = await Student.findOneAndUpdate(
-      { _id: id },
+      { _id: id, teacherId: userId },
       sanitizedBody,
       { new: true }
     )
@@ -65,12 +65,15 @@ export async function DELETE(_req: NextRequest, ctx: { params: Promise<{ id: str
     }
 
     await connectDB()
-    const deleted = await Student.findOneAndDelete({ _id: id })
-    
+    const deleted = await Student.findOneAndDelete({
+      _id: id,
+      teacherId: userId
+    })
+
     if (!deleted) {
       return NextResponse.json({ error: 'Student not found' }, { status: 404 })
     }
-    
+
     return NextResponse.json({ success: true })
   } catch (error) {
     if (error instanceof Error) {
diff --git a/app/api/students/route.ts b/app/api/students/route.ts
index 8f3dcc2..e756d5c 100644
--- a/app/api/students/route.ts
+++ b/app/api/students/route.ts
@@ -84,17 +84,28 @@ export async function POST(req: NextRequest) {
 
   try {
     await connectDB()
-    
+
     let body
     try {
       body = await req.json()
     } catch {
       return NextResponse.json({ error: 'Malformed JSON' }, { status: 400 })
     }
-    
-    StudentSchema.safeParse(body)
 
-    const student = await Student.create({ ...(body as Record<string, unknown>), teacherId: userId })
+    const parsed = StudentSchema.safeParse(body)
+
+    if (!parsed.success) {
+      return NextResponse.json(
+        { error: parsed.error.flatten() },
+        { status: 400 }
+      )
+    }
+
+    const student = await Student.create({
+      ...parsed.data,
+      teacherId: userId
+    })
+
     return NextResponse.json(student, { status: 201 })
   } catch (error) {
     if (error instanceof Error) {
diff --git a/models/Attendance.ts b/models/Attendance.ts
index 3f05fb1..1ead556 100644
--- a/models/Attendance.ts
+++ b/models/Attendance.ts
@@ -17,7 +17,15 @@ const AttendanceSchema = new Schema<IAttendance>(
     teacherId: { type: String, required: true, index: true },
     studentId: { type: Schema.Types.ObjectId, ref: 'Student', required: true },
     studentName: { type: String, required: true },
-    class: { type: String, required: true },
+    class: {
+      type: String,
+      required: true,
+      trim: true,
+      validate: {
+        validator: (v: string) => v.trim().length > 0,
+        message: 'Class cannot be empty',
+      },
+    },
     date: { type: String, required: true },
     status: { type: String, enum: ['present', 'absent', 'late'], required: true },
   },
diff --git a/models/Grade.ts b/models/Grade.ts
index 311b757..e64290e 100644
--- a/models/Grade.ts
+++ b/models/Grade.ts
@@ -39,10 +39,10 @@ GradeSchema.pre("save", function () {
 });
 
 GradeSchema.pre("findOneAndUpdate", function () {
-  const update = this.getUpdate() as Record<string, unknown>;
+  const update = this.getUpdate() as any;
   if (update && typeof update === "object") {
-    const marks = update.marks;
-    const maxMarks = update.maxMarks;
+    const marks = update?.$set?.marks ?? update?.marks;
+    const maxMarks = update?.$set?.maxMarks ?? update?.maxMarks;
     if (
       marks !== undefined && typeof marks === "number" &&
       maxMarks !== undefined && typeof maxMarks === "number" &&