How can we deal with high level students and low level students in a 45 minute period?

I teach90-minute classes so I deal with those the usual way - according to their level, interests and needs

I agree with all answers

Firstly, You need to be very very well prepared, namely, you should  prepare different activities that suit all levels and all tastes to keep the students engaged the whole class.

Secondly, you have to be very well organized so you move from one activity to the other without losing the student's interest and the order in the class.

Thirdly, the students should feel the sense of achievement. So, you should be careful when you choose the activities; the student shouldn't  feel that you as a teacher underestimate their intelligence nor should they feel frustrated due to the over demanding tasks that they cannot achieve.

Last but not least, the class should be fun. 

Differentiation is a key measure. The same objective can be featured in3 different formats. The classroom activities can also be of three levels. For high achievers, they can express and justify their opinion, while for low achievers, they can check their understanding through multiple choice questions. This can be covered by group work of homogeneous groups and the following discussion will ensure that all students learned the same objective, but practiced it according to their performance level.