It is difficult to recommend online science courses at the early high school level without more information.
Is the school situation which you need to solve that in January DS excitedly reported that he had learned something new in science? Are you looking for a replacement for classroom curriculum? Or something for after-schooling to prepare for an out-of-level test?
If looking for a replacement for classroom curriculum, have there been ongoing complaints from DS regarding boredom in science class throughout the school year? Has teacher input at conferences, feedback on tests/assessments, labs or projects, been consistent with a student needing replacement curriculum in the classroom? Are there results from out-of-level tests which would tend to support advocacy efforts in this area?
If concerned that DS recently reported learning something new, is your son especially passionate about a particular unit of science? Are there science topics which he may have studied independently in great depth and breadth over the years, therefore was surprised to learn something new in his area of expertise? While studying science in his classroom do the science topics/units change frequently? Does the syllabus show that he may soon be studying a different topic/unit?
Regarding any online course, are there 2e accommodations which may need to be taken into account in your selection process? Is reading comprehension and science vocabulary at a high school level or above? What grade level is DS currently in? If currently in early high school, what science course is he currently taking... Biology, Honors Biology, Chemistry, AP Chem, Earth Science, Marine Biology, Environmental, AP Environmental, etc?
Sorry that this is not a pat answer, but science is a very broad area and there are many different needs which individual students may have when their families are seeking an online curriculum for them.
Lastly, as you mentioned teaching an online course at the college level, and the fact that quality may vary depending upon the instructor, might your colleagues in online ed be a resource for you in choosing an online science course (and recommending an instructor) at the early high school level?
