We do paid trials (only 1 trial class, at usual cost) - but parents seem to understand that a trial class is pay as you go, and then after that they sign up for the month ... could potentially change to 2 weeks paid trial, but for us it works. Occasionally we offer free trial promotions! This does get more kids through the door. But the retention is less, I believe because they are just turning up for a freebie! ...when they pay for their trial, they are more serious about joining, there's more intent!