例えば、社会科の授業では、先生がメンバーの一人になって、議論がされることがしばしばあります。

、、、。

For example, in social studies class, the teacher often becomes one of the group members and takes part in the discussion.

Literal

For-example, social-studies [of-の] class [in-では], teacher [subject-が] members [of-の] one [to-に] becoming, discussion [subject-が] is-held things-がある often.

議論がされる ('discussion is held') uses the passive of する impersonally — a common formal construction. メンバーの一人になって ('becoming one of the members') is an instrumental action linked by the て-form to the main clause. ~ことがあります is 'there are times when X' — marking something as an occasional occurrence. 教育 register.