The short answer
Classes organised by age band, with the developmental focus of each band explained in one plain paragraph. Parents book by their baby's age, and they want to know why the boundary is where it is.
That is the whole answer. Everything below is how to say it on the page without turning it into a lecture.
How many bands
Most baby class businesses land on three or four for the pre-toddler stage, because the difference between a six-week-old and a ten-month-old is enormous and the difference between two seven-month-olds is not.
A common shape is a non-mobile band, a sitting and reaching band, a crawling band, and a walking or toddler band. Whatever you run, keep the number of bands small enough that a parent can pick hers in one read. Seven finely sliced bands feel rigorous to you and look like homework to her.
Where the boundaries go
Use development, not just months. The honest boundary is the one the room needs: babies who cannot yet move need a calm floor, and babies who can move need space to move in.
So set the band by a range of months, then add the plain-English signal. "From birth to around six months, before your baby is crawling." "From crawling to confidently walking." The month range makes the booking system work. The signal makes the parent confident she has chosen right.
Say the boundaries in months, and let the system check
On the page, give each band a month range. In your booking platform, hold the baby's date of birth rather than an age typed at signup, and let the platform enforce the band. Ages in months go stale within weeks. A date of birth stays true for the life of the record and means the platform can tell you who is about to move up.
Explain the focus of each band
This is the part almost every class website misses, and it is the reason parents message you.
Under each band, two or three sentences on what happens in that class and why. High-contrast visuals, gentle movement and songs for the youngest, because that is what a baby who cannot yet reach responds to. Reaching, textures and cause and effect for the middle band. Space, movement, instruments and simple instructions for the ones on the move.
You do not need to make developmental claims to do this. Describe what happens in the room and what it is for. Avoid anything that sounds like a promise about outcomes, milestones or intelligence, because those claims are regulated as advertising everywhere you operate and none of them are necessary to fill a class.
What to do with a baby on the edge
Every provider gets the same question: she is nearly six months but not crawling, which class do we book.
Answer it on the page before it is asked. One line saying that where a baby is between bands you are happy to advise, and that a trial in either is fine. Then make it easy: a short enquiry route on the class page, or better, a note in the booking flow.
If a baby genuinely straddles two bands and both have space, let her come to whichever suits the family's schedule and say so. Rigidity about a two-week difference costs you a term.
What to do when a baby outgrows a band
The move-up is your best retention moment and the one most often missed.
Set a prompt in your platform for babies approaching the top of a band, and send the parent the next class before she works out that her baby has outgrown yours. If your bands go up to walking and no further, say plainly on the page what you recommend after that, even if it is somebody else. Parents remember who was honest with them, and many of them will be back with a second baby.
What this looks like on the site
The timetable page lists classes grouped by age band, not by day. A parent thinks "I have a four-month-old", not "I am free on Tuesdays".
Each band gets its own short section or page: the month range, the plain-English signal, the focus paragraph, the venues and times it runs at, the price, and a Book a trial button deep linked to that class. The band boundaries on the page match the boundaries configured in your booking platform exactly, so nothing is refused at checkout that the page said was fine.
The one thing not to do
Do not hide the bands behind an enquiry form. "Contact us to find the right class for your baby" reads as helpful and functions as a barrier. A parent who has to ask which class before she can see whether one runs near her on a day she is free will simply check the next provider.
Where this sits
Classes grouped by age band with the focus of each explained, enforced from a date of birth in the booking platform, is one of the first things we build on a baby class website, and the same clarity-before-enquiry pattern runs through our other childcare and family websites. The packages are on pricing. Tell her which class is hers, and why, and she books it.