Do I Need to Change My Child's Behavior?

My son is doing a first grade in a monte city school in our neighborhood. He, by nature, is very shy and takes lots of time to get comfortable and talk to others. Because of cobid, he stayed at home and did a vitual schooling for more than one and a half years. And it's been only a few months he started in person school at this new school. But te school is making his behavior as a big problem and warning us that he will be retained in first grade if he doesn't improve. Instead of really porting and providing extra care to him, they are only dmotivating him by retaining him in the first grade. I'm not sure