Is it permissible to teach children weak hadiths while clarifying their weakness to them, or should they be completely abandoned?

Imam al-Nawawi’s Forty Hadith is a great book, accepted by scholars, and its author is an Imam in Hadith who stipulated that he would only include in it hadith that he considered authentic, and most of them are found in Sahih al-Bukhari and Sahih Muslim. The disagreement of some scholars regarding the authentication of certain hadith within it does not preclude following Imam al-Nawawi, and junior students should not be drawn into these disagreements.