Potty training back to school

So we’ve been potty training all summer, ofc it’s not been going well, my daughters not grasping it (she understands the toilet and hand washing but she doesn’t tell me when she needs to go hence accidents all day) and yes even when I take her toilet every 5 minutes or even every 20-30 minutes she’s holding herself on the toilet and then peeing as soon as we’re out. Anyways, how am I going to handle the school runs and I feel like I’m constantly going to be worrying about her having constant accidents at school? The school understand and have said they think she’s ready and was practicing with her before the summer too but I just can’t grasp the idea that she won’t have constant accidents at school. She’s nearly 4 for reference