"If the training program is organized from a flight syllabus (and it should be), then it is preferable to do flight and ground training concurrently. It helps the student understand the practical application of what is being learned and reduces rote memorization. Most students graduate having fewer flight hours, and spend the least money to certification, when ground is concurrent with flight. Most professionally written, commercially available syllabi (Cessna, Jeppesen, etc.) use this technique — assuming the instructor is using it as designed.