Students rights to dye their hair whatever colour they wished

Students should have the right to dye their hair any colour they wished within reason. Pupils are getting exculed due to 'extreme' hair colour which damage their education more then any hair colour would.

The issue you raise is the responsibility of individual schools and local education authorities, not the UK Government or Parliament. You could start a new petition asking Parliament to create a law that prevents schools from regulating the hair colour of students' hair.