Question

to keep someone on their toes - The new teacher really keeps her classes on their toes. No-one can have a little sleep at the back of the class like before.  - He's starting to get a little lazy - he needs a new challenge to keep him on his toes.  - With Brendan, we worked at a pace that kept us &on our toes, and that's exactly what we needed.  - This defeat at the hands of Nadal is actually good for Federer because it will keep him on his toes.

Accepted Answer

to keep someone working and concentrating

Idiom	to keep someone on their toes
Definition	to keep someone working and concentrating
Examples	- The new teacher really keeps her classes on their toes. No-one can have a little sleep at the back of the class like before. - He's starting to get a little lazy - he needs a new challenge to keep him on his toes. - With Brendan, we worked at a pace that kept us &on our toes, and that's exactly what we needed. - This defeat at the hands of Nadal is actually good for Federer because it will keep him on his toes.

Toes Working Concentrating Teacher Classes No One Sleep Back