Varies enormously between states and school districts.
In our public elementary school, there are two or three options each day: a hot meal of some sort, some days a hot vegetarian meal, and a salad bar that kids can choose what they want from (which usually includes some options that you wouldn't call "salad").
It's not fine dining, but the quality and variety is generally pretty decent. The kids have accounts, and parents are expected to refill a negative balance, but every kid gets the lunch of their choice regardless.
In our public elementary school, there are two or three options each day: a hot meal of some sort, some days a hot vegetarian meal, and a salad bar that kids can choose what they want from (which usually includes some options that you wouldn't call "salad").
It's not fine dining, but the quality and variety is generally pretty decent. The kids have accounts, and parents are expected to refill a negative balance, but every kid gets the lunch of their choice regardless.