To practice counting and writing the numbers to 20 we had an activity with our Math Their Way computation boxes.  There was a  Workjob board with counters on it for each number from 10 to 20. By each board there was a letter.  Our job was to count the markers on each board and write that number by the letter on our record sheet.
 

Besides being  good number counting and writing practice it was also a good activity to help us learn to follow  several directions  at once and learn to organize our materials and work.