Groups have to start at the same time

Note: This article is about groups within one class. If you need two subjects from different classes, please see:
I need subject Math to be on the same position in classes 5.A and 5.B

Now: how to make sure two groups start at the same time:
Please check this picture. It defines that Spanish and German groups will always start at the same time:

Be carefull: in most situtation you don't need to setup this cardrelationship because you assign the lessons to groups and only the groups from the same division can be at the same time. So the software will not put Spanish for Group1 together with PhysicalEducation for Boys. See Divisions

Another wrong usage of this cardrelationship is to prohibit the generator to put Group1 at the end of Monday and Group2 on the end of Tuesday. If you want the children to finish at the same time, you better use the corresponding check box in Class/Details: See Both groups have to finish the education at the same time!

On the other hand this cardrelationship is good when Group1 have Cooking lesson that lasts 3 periods while the Group2 shall have Sewing lesson and then Handworks lesson during this time and the Group2 shall start with Sewing lesson.