When learning to cut curved lines, many children struggle with how far to open the scissors.  Those little hands can have a hard time grading the finger extension required to open the scissor blades.  One way you can help them is to wrap a rubber band around both blades about half way down the length of the blades.  This prevents the blades from opening all the way, while also offering increased proprioceptive feedback for those little hands to be able to better grade their muscle contractions in the future!