Another ridiculous assumption that a toy can fix a lack of concentration!  If a child can concentrate on a fidget spinner, then he/she can concentrate on a math problem, too.  Part of the problem may be one of the difficulty some children who were brought up on tv, cartoons, etc have trouble with the muscle control of their eyes,  There are now "behavioral optometrists" who help parents with kids go back and retrain the child's eyes to be able to read across a page of print or focus on whatever he/she needs to focus on.  

Throughout time, boredom has also been a problem and children will doodle, twirl a pencil or do whatever when bored which is the teacher's job to challenge children individually sometimes and not treat the class as one student working at the same pace.  I know from experience as I tuaght English and Exposition at the secondary level.  My students were on every skill level, but they all needed to learn how to write an effective sentence.