A criminal record is for life. i.e. the offence will always be kept on file. The information will always show up on any CRB check (at whatever level).
For most purposes, offences become 'spent' after a certain period of time, which is defined by the penalty imposed by the court. See here for details:
http://www.lawonthewe...tion_of_Offenders_Act
So (assuming that your brother doesn't receive a prison sentence of over 2½ years) he will eventually reach a point when he no longer has to declare his conviction on most types of employment application, or when applying for things like insurance cover.
However, certain types of employment (and voluntary activities) are excluded from the provisions of the Rehabilitation of Offenders Act. They include working with, or alongside, children or vulnerable adults. When applying for such employment (or activities) convictions are never regarded as 'spent' and must always be declared.
Any application for working with children would require that your brother would have to declare his conviction and that he should also undergo an 'enhanced' CRB check. That would show the 'bare bones' details of the conviction (as would a 'standard' CRB check) but also anything else deemed relevant by a senior police officer (or other relevant authority).
Most criminal convictions don't create an automatic bar from working with children. Even multiple counts of murder, grievous bodily harm and armed robbery would AUTOMATICALLY bar anyone. However the Secretary of State has laid down a rule that anyone who has ever been convicted of a sexual offence against a minor can NEVER be permitted to work with children.
Since any place on a teaching degree course will be conditional upon the student