"What did you do at school today?" Most parents ask this question of their children only to get a "nothing" or "I don't know" response. Children live in the moment so their minds are on what they are doing now rather than what they did earlier in the day. Children also need time to process the events that have taken place. Ask about their day after they have had a chance to have some downtime.
In a Montessori class the children do on an average 6 to 9 works a day. They may eat snack which requires set up and clean up. They also have circle time, story time and play outdoors. That is a lot for a young mind to recall when asked, "What did you do today?"
There is a blog post written by Liz Nieman that has 6 Quick Conversation Starters for Preschoolers. This can be found at http://loveandmarriageblog.com/preschool-conversation-starters/.
Another good question is "Did you have a job today?' In our primary class we have 5 daily jobs. 1)Date the calendar, 2)Feed the fish, 3)Lead the line, 4)Ring the bell, 5)Turn off the lights. These jobs rotate so everyone gets a turn to do each job. Also ask them to "tell me about your day."
We as parents want to know what our children are doing at school. By adjusting our questions we can find out more about their day.