In Texas, teachers are expected to teach the tides, as an example of an observable pattern of change. Of course, understanding the reason for the tides involves a thorough understanding of the positions of the Sun and Moon and of gravity.
5.6 A The student is expected to identify events and describe changes that occur on a regular basis such as in daily, weekly, lunar, and seasonal cycles.
This can be a difficult subject to teach, due to the misconceptions of the motions of the Moon and Sun and of gravity.
In order to understand the causes of tides, students must first understand the causes for Moon Phases: see Modeling Phases.
On the other hand, to learn that the tides are cyclical and repeat twice a day, students should engage in an observational activity, preferably working with data to graph the tides.