All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
There is no blame on you to use human images/illustrations within school textbooks to teach Islamic morals as long as there is no other way to achieve such a goal. But you have to efface countenance in such a manner that no one can recognize eyes, nose or mouth. In addition, one should not resort to such a way of teaching except in case of need and on a limited scale. Such images and illustrations should not include any prohibited things such as cross or immoral images.
At the same time, if one finds some other permissible ways to teach Islamic morals, then one is not allowed to use images and pictures.
Here, prohibited images and illustrations mean those of living creatures drawn by hand or three-dimensional pictures.
Pictures and images of trees, stones, rivers, mountains and so on, are permissible as long as they don't include a living creature such as man, animal or bird.
As for photography, in accordance with the more correct opinion among Muslim scholars, there is no blame on you to use such pictures for permissible needs, be they of living creatures or inanimate being.
For more benefit on making images, please refer to Fataawa 88456, 4549, 63235, 89555, and 88306.
For more benefit on drawing images without the eyes, nose and mouth, please refer to Fatwa 380557.
For more benefit on making 3D animations as part of one's study, please refer to Fataawa 310936 and 351178.
Allah knows best.