The Sherwood Library, bless them, supports six children's programs each week (not counting the summer reading program). We now have one Baby Time, three Toddler Times, and two Preschool Storytimes. Parents often wonder which one their child should attend, which are the most crowded, and whether there are differences among them. Here is my answer.
Baby Time is for babies as young as you want to bring them, up to the time they are more interested in exploring than sitting in your lap. Of course, that will be different for each child, but this is what I've learned are the patterns.
Because very young babies don't have good muscle control in their necks, the bouncing movements that go along with our rhymes and songs won't be appropriate for them. Once they have good control, they're ready to enjoy the program. We do bouncy songs and rhymes, play with manipulatives, do Ring Around the Rosie (in the parent's arms) and blow bubbles, among other things. Babies love it, usually until they are walking (or really fast crawlers). Then they realize they don't have to sit in one spot, and the other babies and the chairs and toys are much more interesting than a lap. That seems to be around 12 months.
Toddler Time is "marketed" for ages 18 months to 3 years, but many toddlers come earlier than 18 months, and that's fine with me. If they enjoy watching the children, absorbing the songs and rhymes, and interacting with the adult who brings them, then they're learning and getting a lot out of it. They'll be up an participating in no time. We do movement based songs, fingerplays, two stories, one lap activity, and a song with a manipulative such as pompoms or maracas. It's very high energy.
After they turn three, they can start transitioning to Preschool Storytime. Some children are ready for a more literature based program when they turn three, but others aren't ready to sit still for as long as I ask. However, during that transition time it's fine to bring Jacob or Emily to Preschool Storytime for as long as they are willing, whether it's ten minutes or twenty. It doesn't have to be an "all or nothing" change, so it's okay to leave before the program is done. Once they turn four, Preschool Storytime is the right place for them.
At Preschool Storytime (sometimes called "Big Kid Storytime") I usually have four or five books, one of which is a flannelboard or puppet story, or movement based. I always have a wiggle-buster or two thrown in so the kids don't have to sit still the whole time. They never have to sit for more than two books in a row. Each week I have a theme, like Ocean (this week) or Bears, or Naughtiness. I don't do crafts - sorry. There are just too many good books out there to take the time. Besides the fact that I'm just not very good in that department.
FYI, the Tuesday Toddler Time and Preschool Storytime are definitely the most crowded. Wednesday, they're both smaller, and the Thursday Toddler Time is the smallest. You can look at the library website for days and times or pick up a calendar at the front desk, which also lists the themes for each week.