How to escalate cases using Apex in Salesforce?

Sample Code:

Batch Class:

global class CaseEscalation implements Database.Batchable <sObject>{
    global Database.QueryLocator start(Database.BatchableContext bc){
        String SOQL = 'SELECT Id, IsEscalated FROM Case WHERE Status = \'High\' AND IsEscalated = False';
        return Database.getQueryLocator(SOQL);
    global void execute(Database.BatchableContext bc, List<Case> caseList){
        for(Case c : caseList){
            c.IsEscalated = true;
        update caseList;
    global void finish(Database.BatchableContext bc){

Schedulable Class:

global class CaseEscalationSchedule implements Schedulable{
    global void execute(SchedulableContext sc){
        CaseEscalation ce = new CaseEscalation();