"I just want to say it looked incredible," Weaver said to the students in a video posted to Facebook.
"The alien, I must say, looked very real to me."
She added that she was also speaking on behalf of director James Cameron and Walter Hill, who wrote the screenplay for the film.
Weaver played Lt. Ellen Ripley in the original film and in a number of sequels.
The school's play, which featured DIY sets of the spacecraft and a costume depicting the titular space monster, drew rave reviews after images of the elaborate production went viral online last week.
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