[quote=@GreenGoat]
Yes. Its very unlikely to have Varus with his super emotion blast explosion to have the composure to develop a protective shield with his ability. So its either an enchantment on the grounds itself, another effect from the poison the headdudeman poisoned the students with, or a powerful ESPer in the school itself.
[/quote]

Could be innate magic stuff by the kids. You know? Cause magic. Or something. At least, I'd assume that's why they're all out despite not having any external injuries. And also why Varus didn't simultaneously expel the entire year level.