XPath to get the maximum ID

XML Source:

<schools>
    <school>
        <name>School A</name>
        <student>
            <name>Student A</name>
            <id>12345</id>
        </student>
        <student>
            <name>Student B</name>
            <id>45678</id>
        </student>
    </school>
    <school>
        <name>School C</name>
        <student>
     开发者_如何学编程       <name>Student C</name>
            <id>91178</id>
        </student>
        <student>
            <name>Student D</name>
            <id>99999</id>
        </student>
    </school>
</schools>

I am still a beginner to XPath. I want to get the student with the overall highest ID (so 99999 in the example), not from each school. I can't change my python code which is

tree.xpath(" ... ")

I can only modify the xpath. I have tried "//student[not(../student/id > id)] but this gives me highest id students from respective schools. What I want is the overall highest ID. How should I modify my xpath?

Edited : How do I write starting from the school level? I mean what if I want the school name which "highest ID" student exits?

What about:

//student[not(../../school/student/id > id)]

Or, more simply:

//student[not(//student/id > id)]

To get the <school/> element with the highest student ID, I believe this will work:

//school[student[not(//student/id > id)]]

Use:

/schools/school[student[not(../../school/student/id > id)]]/name

Or shorter (just for this schema):

/*/school[*/id[not(//id > .)]]/name

Just for completeness... If you could had XPath 2.0 available, you could use max(), as in:

/*/school[*/id = max(//id)]/name

It's a little easier than in XPath 1.0.

However AFAIK you do not have XPath 2.0 available in Python. So go with @cdhowie's or @Alejandro's answer.