My niece went to Cherie Hearts in the East Coast, and we found the quality of the teachers terrible! So we took her out and sent her to Pat School House instead.
You can find good quality leather black school shoes for international school at Shooz 4 Kidz. The store is located in United Square shopping mall, near Novena MRT, which is 5 mins from Orchard Road.
I personally don't like Clarks and Stride Rite. Their shoes are made of inferior quality leather, and most of their shoes don't even come with leather insole. Also a lot of their shoes are made of synthetic material. Check and ask the store assistant about the material of the shoe before buying.
You can check out Shooz 4 Kidz at United Square. They sell nice and good quality leather shoes, imported from Spain Italy and USA. I always shop there as they carry the largest selection of kids shoes.