从中囯来美国读高中的小留学生，F1签证今年七月过期，护照还有三年有效期。
因为疫情和大使馆是否正常运行，担心如果夏天回国可能拿不到新签证。如果不回中国，留在美国读剩下的两年高中，合法吗？
-Yes. The visa stamp is just used for the entry to US, not related to the legal stay in US. So, its expiration does not matter.
学校会发I-20，需要什么手续才能在美国合法地继续上完高中？
-Continue to study in the school as a full-time student. Talk to the school to extend the I-20 if it will expire soon. Bty the way, the child only can study in a public high school for one year. So, if he/she has studyed in a public school for one year, he/she has to transfer to a private high school (do F-1 transfer).
希望懂的人愿意帮我回答，谢谢
