Students perform exercises for self-assessment or in the context of an assignment. In both cases, the teacher can show or hide the solutions of the exercises to their students, as long as they are connected to them.
The customisation of the display of solutions 
to students is done on three (3) levels.
Level 1:
When the student solves an exercise on their initiative, the book shows, next to the Submit button, an additional Show Solutions button to help them in the context of self-assessment. If you (as an educator) do not want this button to appear on your student, Open the lesson 
, click on the Students 
in the book, and select Hide solutions
for one or all students. The Show Solutions button will no longer appear.
When sending assignments, you can set the Hide solutions mode on each assignment individually.
Level 2:
When a student performs an exercise and clicks Submit, the book displays the total number of correct answers (e.g. 3 out of 10 correct answers) while differentiating correct and incorrect answers by color on the spot. If you do not want the colour differentiation of the result to be displayed as information to the student, find the tab of the lesson you are interested in on the MY LESSONS shelf and click on the Setting Solutions icon. Uncheck the Level 2 solutions display.
Level 3:
When the student has already performed an exercise, they can enter their stats by clicking on the Open lesson icon and then on the Statistics 
icon in their book. There the learner can see an overall total (in % percentage) of the correct answers they gave and review their effort by checking the relative color differentiation for correct and incorrect answers. If you (as an educator) do not wish the colour differentiation of the result to be displayed as information to the student, find the tab of the lesson you are interested in on the MY LESSONS shelf and click on the Setting Solutions icon. Uncheck the Level 3 solutions display.
Suggestion:
To avoid making different settings for each lesson, you create a default setting for all lessons. Open the General Settings 
in the top right of the main screen, click Solutions and customize as you wish to. This will exclude those for which you have enabled personalised customisation.
Frequently Asked Questions (FAQ)
Question: Why should I hide the solutions from the students, since I can always see in their statistics who clicked earlier to see the solutions and who did not, or who already performed an exercise as a self-assessment that I sent later as an assignment?
Answer: the choice is purely subjective and depends on the objective of the lesson, the age, level, and impulsiveness of each student. In general, it is observed that when your students know that you have a full picture of who sees the solutions before or during the execution of an assignment, they do not make inappropriate use. The relevant teacher information includes; a) accurate recording of the date and time the student views the solution in their stats and b) recording of the date and time when the student has viewed the solutions in the context of self-assessment.
In any case, if the purchased textbook you are teaching contains extra material for educators, you may send new exercises, unknown to the students, that are only communicated to them in the context of assignments. You can also hide the solutions in each lesson, at one or all levels.
Note that if you are using the notebooks you created for the lesson, you can choose to partially hide their contents in the same settings tab by clicking Manage Visibility of notebook Contents. Students will not be able to see, for example, the contents and exercises of the upcoming week.
Question: I do not see nor can hide the contents of my notebooks for my lesson’s purposes.
Answer: The contents of your notebooks must be declared accessible to your students in the authoring tool you created them. Check the green boxes when editing your notebook in the authoring tool. See paragraph 3.5 for further clarification and instructions.