node.js update of mongoDB problem...

I am doing a node.js and mongo assignment...
The test is to loop through a mongoDB find the lowest grade scores, and remove them.  I was able to write something that would find the lowest grades, remove them from a secondary var with splice()
but now I want to update the original document with the new array... and this is the part I am having difficulty with.

the first code is really just the PRETTY() version of some mondodb records that I am querrying... the SCORES array is the important part.
The second program will create a doc and doc.scores with the corrected data.  But I am trying to update the original DOC with the new data.  Not sure how to do this.

~~~
> db.students.find({_id:113}).pretty();
{
	"_id" : 113,
	"name" : "",
	"scores" : [
		{
			"type" : "exam",
			"score" : 77.57315913088024
		},
		{
			"type" : "quiz",
			"score" : 13.28135073340091
		},
		{
			"type" : "homework",
			"score" : 67.27527802263116
		},
		{
			"type" : "homework",
			"score" : 55.74198976046431
		}
	]
}

~~~

my program would splice out doc.scores[1] which has the lowest score.

Now I want to update the original db.  My code is below...


~~~

var MongoClient = require('mongodb').MongoClient;
MongoClient.connect('mongodb://localhost:27017/school',
                    function(err, db) {

                     if(err) throw(err);

                      var cur = db.collection('students').find({}).sort({name:1});
                      var updates = 0;
                      var curDone=false;
                      cur.each(function(err, doc){
                        if(err) throw err;
                        if (doc != null){
                          console.dir(doc._id + "--  record "+ doc.name);

                          zz = doc.scores;
                          zzlowScore = zz[0].score;
                          zzlowScoreIndex = 0;
                          for(var i = 0, l = zz.length; i < l; i++ ){
                            console.dir("========zz--Index "+i+" ---  score: "+ zz[i].score);
                            if(zzlowScore > zz[i].score){
                            //we have a new low score and index
                                  zzlowScore = zz[i].score;
                                  zzlowScoreIndex= i;
                                };
                          };

                            console.dir("===  low score Index "+zzlowScoreIndex + "  ==lowscore== "+zzlowScore);

                            console.dir("..............remove the bad stuff..."+ doc._id);
                            doc.scores.splice(zzlowScoreIndex,1);

                          zz = doc.scores;
                          for(var i = 0, l = zz.length; i < l; i++ ){
                            console.dir("====zz--Index "+i+" ---  score: "+ zz[i].score);
                              };
console.dir("============================================================================");
                            //doc.update({_id:doc._id},{scores:zz});
                            //db.collection('students').update({_id:doc._id},{scores:zz});
//
//Now I need to pass the new doc.scores back to the DB so it can update scores subarray.
//But not sure how to do this.



//cur.update({_id:doc._id},$set:{scores:zz});
db.schools.update({_id:doc._id},$set:{scores:zz});
//!!!!!!!!!!!!!!   THIS IS THE PART I CAN NOT FIGURE OUT.  HOW TO UPDATE ORIGINAL DOC??????

//return doc.scores;

                        }else{
                          db.close();
                        };


                        console.dir("++++++++++++++++++++++++++++++++++++++++++");


                      });
                    });


~~~