Patience is key to supporting children who are struggling with a certain school subject. It's easy to expect instant gratification, but sometimes it takes a long time and a lot of practice to master a skill.
It's also important not to get frustrated in our ability to teach, because a child can feel the frustration from his parents/teacher, which only makes it worse. Instead, I always try to give the subject a break for awhile and then present the material in a new and fun way. Whether it's using fun terminology (like saying a number is jumping or that two numbers are dancing together), inventing a game, finding a hands-on activity, or combining it with a subject the child really enjoys.
Sometimes when we start fresh and demonstrate the work in a new way, it clicks in the child’s mind and leads to a sensitive period. It also doesn’t hurt to add an element of fun!