Double Trouble by Michael J. Pellowski, 1986.
Sandi and Randi Daniels are identical twins with a younger brother, Teddy, who is in his Terrible Twos. Although Sandi and Randi look alike, they are still very different people. Sandi loves to read and is a good student, and Randi is loves sports, especially soccer. The problem is that Randi’s place on the soccer team is in danger because of her poor grades. Their father has told her that if she doesn’t improve her spelling, she won’t be able to play soccer anymore, and the championship game is coming up!
The two girls come up with a possible solution to the problem when Teddy accidentally mistakes Sandi for Randi one day because Sandi is wearing her sister’s favorite shirt. Since Sandi is much better at spelling than Randi is, Sandi will dress as Randi and meet her teacher for her special tutoring in spelling while Randi goes to play soccer with her sports team.
But, everything goes wrong when Randi’s coach talks to her teacher about the championship game, and it turns out that her teacher is secretly a soccer fan. When Sandi arrives for the tutoring session and the teacher and coach tell her the happy news that “Randi” can play in the championship game, Sandi has no time to tell Randi about it and switch places with her again. Will their hoax be exposed? Will the girls be able to switch places again in time to save the championship?
There are black-and-white drawings throughout the book. This is the first book in a series.