1. It's essential that he come. Correct. This is a correct subjunctive form, but it is fairly formal. Don't be surprised if the average English native speaker assumes it's a mistake and tries to correct it to 'that he comes'. 2. It's essential that he should come. Correct. This is a more everyday alternative to the subjunctive form above. It's a kind of 'informal subjunctive. 3. I think that it is vital that she go to a good school. Correct. As with number 1 above, it's a correct but fairly formal-sounding subjunctive. In everyday English, we tend to either go for the compromise of 'that she should go..' or simply use an indicative '..that she goes'. This avoidance ( and in most cases ignorance) of the subjunctive mood is very common, especially in British English. American English speakers are more formal in this respect, and will often use a correct subjunctive where their British counterparts use a lazy indicative. 4. I wish I didn't have to go to work tomorrow. Correct. We do use a subjunctive following 'I wish...' even in everyday English. Even people who have no idea what the subjunctive mood is would still instinctively use the correct form.

It's essential that he should come = Correct It's essential that he come = It's essential that he came or it's essential that he comes (depending on context) I think that it is vital that she go to a good school. = I think that it is vital that she goes to a good school I wish I didn't have to go to work tomorrow. = Correct

I believe they are all correct.