Time needed: 45 to 90 min
Why? First hand information is exciting and authentic. Guests will leave an impression and content they tell will create a big affect. It creates a lively, emotional atmosphere and gives your students the feeling of an open school.
When? Whenever you know someone to invite, do it.
How? You invite a person to come to your class. It could either be an expert, or someone famous, or someone who experienced something special. Give a short introduction and let her or him talk.
Any risks? Talk with your guest about content and procedure beforehand. Make sure she or he knows the target audience, your students, their age and background. Tell your guest if your students are familiar with the topic or not. Watch out for any political agenda the person might have and prepare students for that.