6. (6 points) The zodiac signs of the students in a school include Rat, Ox, Dragon, Snake, Horse, Sheep, Monkey, Rooster, Dog, and Pig. Then, at most how many students need to be selected to ensure that two students have the same zodiac sign.

将上面的文本翻译成英文，请保留源文本的换行和格式，直接输出翻译结果。

---

6. (6 points) The zodiac signs of the students in a school include Rat, Ox, Dragon, Snake, Horse, Sheep, Monkey, Rooster, Dog, and Pig. Then, at most how many students need to be selected to ensure that two students have the same zodiac sign.
【Analysis】Establish drawers: Consider the zodiac signs Rat, Ox, Dragon, Snake, Horse, Sheep, Monkey, Rooster, Dog, and Pig as 10 drawers. Use the pigeonhole principle to consider the worst-case scenario to solve the problem.

【Solution】Solution: Consider the zodiac signs Rat, Ox, Dragon, Snake, Horse, Sheep, Monkey, Rooster, Dog, and Pig as 10 drawers. Consider the worst-case scenario: select 10 students, each placed in one of the 10 drawers. Then, select any 1 more student, and no matter which drawer they are placed in, there will be a drawer with 2 students.

So, $10+1=11$ (students),
Answer: At most, 11 students need to be selected to ensure that there are two students with the same zodiac sign.
Therefore, the answer is: 11.