diff --git a/app/api/register-school/route.ts b/app/api/register-school/route.ts
index e60637d..e17071c 100644
--- a/app/api/register-school/route.ts
+++ b/app/api/register-school/route.ts
@@ -301,13 +301,17 @@ export async function POST(request: NextRequest) {
       );
     }
 
-    // 4. Insert instructor
+    // 4. Insert instructor — de registratie-oprichter is de beheerder van de
+    // nieuwe school en wijkt daarom bewust af van de veilige DB-default
+    // school_role='employee' (die default beschermt alle overige aanmaakpaden,
+    // zoals invites).
     const { data: instructor, error: instructorError } = await supabase
       .from('instructors')
       .insert({
         user_id: authUserId,
         drivingschool_id: school.id,
         status: 'active',
+        school_role: 'admin',
       })
       .select('id')
       .single();
diff --git a/tests/register-school-admin-role.test.mjs b/tests/register-school-admin-role.test.mjs
new file mode 100644
index 0000000..56caa98
--- /dev/null
+++ b/tests/register-school-admin-role.test.mjs
@@ -0,0 +1,125 @@
+// register-school — pint vast dat de REGISTRATIE-OPRICHTER als school-admin
+// wordt aangemaakt (correctie 21 jul 2026). Sinds F3.1A is de DB-default
+// voor instructors.school_role de veilige 'employee'; alle rolgevoelige
+// domeinen (financiën, Stripe Billing Portal) zijn admin-only. De oprichter
+// van een nieuwe school moet die rol dus expliciet meekrijgen — anders is
+// een via de web geregistreerde school direct beheerder-loos. Invite-paden
+// blijven buiten dit bestand: die maken hun instructeursrijen in ribbaPro
+// aan en behouden daar hun bestaande rolgedrag (default employee).
+
+import { test, mock } from 'node:test';
+import assert from 'node:assert/strict';
+
+process.env.NEXT_PUBLIC_SUPABASE_URL = 'http://localhost:54321';
+process.env.SUPABASE_SERVICE_ROLE_KEY = 'test-service-role-key';
+process.env.NEXT_PUBLIC_BASE_URL = 'https://preview.test';
+delete process.env.RESEND_API_KEY; // e-mailpad slaat dan netjes over
+
+const inserts = []; // { table, payload }
+
+function makeFakeSupabase() {
+  return {
+    auth: {
+      admin: {
+        generateLink: async () => ({
+          data: {
+            properties: { action_link: 'https://verify.test/confirm' },
+            user: { id: 'auth-user-1' },
+          },
+          error: null,
+        }),
+        deleteUser: async () => ({ error: null }),
+      },
+    },
+    from(table) {
+      return {
+        // slug-uniekheidscheck: geen bestaande school gevonden
+        select: () => ({
+          eq: () => ({ maybeSingle: async () => ({ data: null, error: null }) }),
+        }),
+        insert(payload) {
+          inserts.push({ table, payload });
+          return {
+            // pad mét .select('id').single() (drivingschools/instructors)
+            select: () => ({
+              single: async () => ({
+                data: { id: `${table}-1` },
+                error: null,
+              }),
+            }),
+            // pad dat direct ge-await wordt (licenses/invitation_links)
+            then: (resolve) => resolve({ data: null, error: null }),
+          };
+        },
+      };
+    },
+  };
+}
+
+mock.module('@supabase/supabase-js', {
+  namedExports: { createClient: () => makeFakeSupabase() },
+});
+mock.module('next/server', {
+  namedExports: {
+    NextResponse: { json: (body, init) => ({ body, status: init?.status ?? 200 }) },
+    NextRequest: class NextRequest {},
+  },
+});
+mock.module('@/lib/rate-limit', {
+  namedExports: { rateLimit: () => true },
+});
+mock.module('@/lib/admin-notifications', {
+  namedExports: { sendAdminNotification: async () => {} },
+});
+mock.module('@/lib/legal-acceptances', {
+  namedExports: {
+    recordLegalAcceptances: async () => {},
+    pickAcceptedVersions: (_v, types) =>
+      types.map((t) => ({ document_type: t, document_version: '1.0' })),
+    extractIpAddress: () => '127.0.0.1',
+    extractUserAgent: () => 'test',
+  },
+});
+
+const { POST } = await import('../app/api/register-school/route.ts');
+
+function makeRequest() {
+  return {
+    headers: { get: () => null },
+    json: async () => ({
+      legal_form: 'eenmanszaak',
+      country_code: 'NL',
+      school_name: 'Rijschool Oprichterstest',
+      first_name: 'Anne',
+      last_name: 'Oprichter',
+      email: 'oprichter@example.com',
+      phone: '0612345678',
+      address: 'Teststraat 1',
+      postal_code: '1234 AB',
+      city: 'Teststad',
+      kvk_number: '12345678',
+      password: 'wachtwoord123',
+      legal_acceptances: { terms: '1.0', privacy: '1.0', dpa: '1.0' },
+    }),
+  };
+}
+
+test('registratie-oprichter wordt aangemaakt met school_role=admin', async () => {
+  inserts.length = 0;
+  const res = await POST(makeRequest());
+  assert.equal(res.status, 200);
+
+  const instructorInserts = inserts.filter((i) => i.table === 'instructors');
+  assert.equal(instructorInserts.length, 1); // precies één instructeursrij
+  assert.equal(instructorInserts[0].payload.school_role, 'admin');
+  assert.equal(instructorInserts[0].payload.user_id, 'auth-user-1');
+  assert.equal(instructorInserts[0].payload.status, 'active');
+
+  // De multi-use uitnodigingslink van de school blijft een leerling-invite;
+  // dit pad kent geen rol-parameter en blijft dus op het bestaande gedrag
+  // (instructeurs via invites krijgen in ribbaPro de veilige default).
+  const inviteInserts = inserts.filter((i) => i.table === 'invitation_links');
+  assert.equal(inviteInserts.length, 1);
+  assert.equal(inviteInserts[0].payload.invite_type, 'student');
+  assert.equal('school_role' in inviteInserts[0].payload, false);
+});