you could say to the student with the green t-shirt:
"You're very communicative and fun. It would be great if you showed more confidence, because it would make you more effective! [to all students] Don't be shy, making mistakes is normal".
"You're very communicative and fun. It would be great if you showed more confidence, because it would make you more effective! [to all students] Don't be shy, making mistakes is normal".
