To easily update leads entry year and year level by one year you can utilise the Roll Up functionality.
The Roll Up option sits within the bulk actions Edit dropdown on the Leads table.
Simply select the checkbox or boxes alongside one or multiple leads, select edit and select Roll Up Year Level and Entry Year. The below modal will appear for your review and confirmation.
One year will be added to the entry year and year level of any leads you have selected to apply this action to.