Из active voice в passive voice
1)They discuss different problems at the lessons.
2)the builders built a new school.
3) pupils must take exams at the end of each stage of education
4) they will know the result of the tests in a few days.

1 Different problems are discussed at the lessons2 A new school was built3 Exams must be taken  at the end of each stage of education4 The result of the test will be known in a few days