My mum stays in Yishun too. At first, I sent my gal to a childcare in Yishun, but later found unsuitable for her. I checked several childcare around Yishun but dont't like it. I have then sent my gal to Emmanuel Child Educare behind Sembawang Shopping Centre. She's was there since Nursery, now K1. I can say I'm satisfied with what the school has provided.
After school, schoolbus will pick her around 5 pm to my mum's place. You may wish to visit the centre.