Looking for children's book author, read in the '80s, probably much older

[Rick]

I remember bits and pieces of individual stories from books by this author, and I read them while in elementary/middle school in the early to mid '80s. I'm guessing they were written in the '50s or '60s.

I do remember it was a female author.

Some of the storylines I remember:
Identical twin boys were included in the characters, and at one point one of them had to have their hair shaved due to something being stuck in it. When his hair grew back, it was curly unlike his twin's, so people could now tell them apart.

A new kid named Sydney moved into the neighborhood during the winter, and until she took off her cap in the Spring, no one knew she was a girl.

A shop had a contest to guess the number of gumballs in a jar. They all paid money and tried to guess, but failed. The much younger brother of the main character guessed "one, two, three, four" and won.

Anyone have any guesses?

[Lobstergirl, au gratin]

Rick, please add some of those plot lines to your topic header (use the edit link). This makes searching for your book easier.

[Ember]

This might be too recent, and I'm not sure on the details, but could it be the author Louis Sachar, and maybe his Sideways Stories from Wayside school books?

[Kris]

Rick, are you still looking for this book or did you find it?