Personally, I find the ambiguity of "they" to be more due to "Ministry of Education" than "TV programmes". While "Ministry of Education" is semantically singular, it refers to multiple people, so it would not be odd, especially in BrE (which the spelling "programme" implies you are speaking) to refer to it with a plural pronoun. A careful reading would allow one to conclude that the students attending lectures makes more sense than people in the Ministry of Education doing so, but clarity means not making your readers work hard at figuring out what you're saying.
A further problem is saying "attend these lectures" to refer to "TV programmes". One attends lectures, but one does not attend TV program[me]s, so using that verb is jarring, and works against the reader recognizing that "these lectures" refers to "TV programmes".
Your use of passive voice contributes to the problem, as it puts "Ministry of Education" next to "high school students". Switching to active voice would allow you to move "Ministry of Education" away from "high school students" and combine the two parts of the sentences, avoiding the duplication of "students".
Also, at least in AmE, "school" is generally treated as an abstract noun, and thus doesn't take a grammatical number. Even when different students are going to different school, we say "Students are going to school", not "Students are going to schools", unless there's a specific reason to talk about different schools.
There may be some purpose in the larger context, but looking at just this sentence, I don't see much purpose that "There are" at the beginning is serving.
Putting all of this together:
The Ministry of Education has produced TV programmes that high school students can watch remotely instead of traveling to school.