For a couple of years now we have used the Grow Veg online planner to plan out our plot. This is a simple to use planning tool that could be used at all levels in school as well as for adult gardeners.

It also alerts you if you try and grow a similar crop in the same position in subsequent years. Plans can be printed. As well as offering an online planning tool for a small annual subscription of £15/€17 (There is a North American version too) the website has advice and tips for growing all types of vegetables.
This planning tool has proved very popular in some schools and a school licence is available which allows a single account to be used by multiple pupils or groups of pupils in a class. This is basically the same as a single-user account but is marked for concurrent access. It costs £25 per year (which can be invoiced to the school if required). The teacher will usually set up the plan for the garden as a template that they then copy over for each child/group. The pupils are all logged on to the same account but open the plan allotted to them so that they don't save over each other's work. Setting it up this way enables the teacher to log on and get access to all the pupils' plans after the class. For more information use the contact button on their website. Please refer to this website when you do so.
A demo of the online planner can be viewed on their website and if you fancy having a go a 30 free trial is also available. To learn more click on the banner below.
More suggestions for ICT activities are available on my website here