Dd (4) starts every day with 'I don't want to go to school, I don't like school, you're a bad mummy, school is scary..' Every morning its a battle to get her out of the door. Dp and I work, so we're not picking her up most days, which adds to the guilt.
I suspect she's ok when she's there, plays with friends, enjoys doing stuff (from the titbits she drip feeds me). But she's undeniably anxious (chewing hair/fingertips, constipated etc) and tired.
Foolishly we thought she'd be fine as she was in full time nursery (and loved it) and she skipped happily into school the first two days. Little did we know. She keeps asking me if its Saturday yet...
It does get better but it can take time. My kids found Yr 1 particularly hard. In the end what helped was consistency from me in just quick cuddle, saying good bye and cheerful wave off, sticker chart from teachers and at one point going in through office rather than parting at classroom as they had come to associate it with crying. It's early days yet. Stick with it. I sympathise though - it's as hard for the mum as it is for the kids. Maybe worse?!
Mine used to do this. He was at full time nursery as well. It's a bit of separation anxiety mixed in with a big change in their life and lots of new people and new environment. But it's life and they'll get there.