Note learning worksheets (ideally in German)

Hi fellow piano teachers! I teach at several private music schools in Germany and have just started back up this week with all new-to-me students (mainly kids aged 6-11). An issue I’ve noticed is that many of them, even ones who have been taking lessons for a year or more, still really struggle with note reading. Does any one have any worksheets or books to recommend to help with this? I also teach mostly in German, so ideally German-language worksheets would be great. Also just any resources, especially ones that make it fun to learn notes. I barely remember learning to read music since I started so early - all I remember is coloring in notes that formed pictures. Thank you all for your help! Happy school start!