The website Aplicaciones Didácticas has a collection of short Spanish readings for children. The readings have comprehension questions that can be answered online, or you can print the reading and questions.

The 40 Spanish readings are not arranged in order of length or difficulty. Some of them are very simple and appropriate for many language learners, so it is worth reading several to find the ones that work for you. There are a variety of topics, but all of the stories are short, with little detail. Most of the comprehension questions are taken directly from the readings, so children do not have to infer the answers. There are four or five multiple choice questions for each reading.

These readings can be very useful for teachers and parents looking for extra Spanish reading material. Several of the stories will be familiar to children, although they are told in a very abbreviated form. The stories are not illustrated, so children may want to draw their own pictures. They can use their illustrations to talk about the characters and retell the story in their own words.

Note: In reading #2, Marcelino, pan y vino, each sentence appears twice. The other selections that I have read are fine.

Link to Spanish Reading for Kids:

Spanish Reading with Comprehension Questions from Aplicaciones Didácticas

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Online Spanish Resource for Teachers and Parents - ARASAAC
Spanish Reading Resources for K-6 from MacMillan/McGraw-Hill