We do randori at the first lesson, then in each lesson following that one. We do it all the time. Randori is done in each and every test we do. Generally both at the start and the end of the grading. Most of the time, expect to do about 4 or 5 rounds both as uke and tori.
Check out my posts on randori as I have made several. Kakari geiko -> hikitate geiko -> softo randori -> randori -> shiai is the general progression we use.