My DS had a new teacher in September (Year 5). Its a small class of only 22. She calls him, and the others, by other childrens names, some not even in their class. When he doesn't respond to her because she has called him someone elses name she gets cross and deducts team points/golden time etc
How long does it usually take a teacher to learn childrens names? I don't want to go into school and ask about it if it's not unusual to not know their names until after half term/later in the year. This has never been a problem with any of my other DC's 
Would as a teacher you think I'm being cheeky if I sent him wearing a name badge until she starts calling him by his actual name?