Crocs or Toms. You want something with a rubber bottom for fire drills and such, plus they will be more likely to last the whole year.

Any type of slip-on shoe, crocs, slippers. Just make sure they'll stay on when your kid is active/running indoors.

Do they allow Crocs? That's what we used for my kid's indoor shoes at preschool this past year and she could easily get them on/off herself.

There are also Montessori shoes which are softer/quieter, but the appropriateness depends on the school environment. If other kids are running around in outdoor-style hard-soled shoes, you don't want your kids feet getting unintentionally stomped on.

Just get a pair of his outside shoes that you know fit well but use them for indoors only.

My 4 year old is starting nursery school soon and they are requiring an indoor only pair of shoes. He has wide,m feet that are also puffy on top, so an adjustable strap or similar style would be good. Any good recommendations? We tried Target and Walmart and couldn’t find anything, so probably will need to order from Amazon and try a few sizes.