What one should make of Paul the schoolteacher is uncertain, but one possibility is that proclaiming the gospel in traditionally religious spheres was so ineffective that he turned to the educational arena. I have participated in some very successful gospel meetings. In every case, the local preacher had a number of persons prepared, so that a minimum of proclamation coupled with persuasion would reap the harvest. Evangelism is not only reaping. Evangelism is plowing, sowing, and watering.
Evangelism is a process.
Premature reaping is disastrous. We tend to try to emulate Paul, but miss an important element from the picture portrayed in Acts. We think that if we could just get every person on the face of the earth to hear the gospel one time, our job would be done. If we could in fact achieve this worthy goal, our job would only be begun. Churches would be established, spiritual centers from which the gospel could spread would spring up in many places.