This is the version I learned as a recitation in school in Dublin in the fifties.

Twenty froggies went to school,
Down beside a rushing pool,
There the teacher master frog,
Sat all day upon a log,
Their they learned a lot from him,
How to dive and how to swim.
Twenty froggies grew up fast,
And became big frogs at last,
Now they sit on other logs,
Teaching other little frogs.

Fergus